The reward for 7th grade math problems is 15 points, and the reward for 7th grade math problems is v

1.Let the single digit be x, then the ten digit is x+1, and this two-digit number can be expressed as 10 (x+1)+x, that is, 11x+10, from 30<11x+10<42 and x is an integer, the solution is x=2, and the two-digit number is 32

2.3x+a=x+7 => 2x=7-a => x=(7-a) 2 is a positive number: x=(7-a) 2>0 => a<7

3.ax>2x+5 => (2-a)x<-5 , when a<2, 2-a>0, so => x<-5 (2-a) is the solution set.

4.3x-m<=0 gives x<=m 3 Because the positive integer solution is , so 3<=m 3<4 (Note: Equal to 4 cannot be taken here, because it is equal to 4, then the positive integer solution can also be taken as 4, which does not meet the original conditions), and 9<=m<12, so the value range of m is [9,12).

1.32 (if the ten digits are 4, the single digit is 3, and the resulting 43 is greater than 42 does not meet the requirements).

2.3x+a=x+7 => 2x=7-a => x=(7-a) 2 is a positive number: x=(7-a) 2>0 => a<7

3.ax>2x+5 => (2-a)x<-5 , when a<2, 2-a>0, so => x<-5 (2-a) is the solution set.

4.3x-m<=0 gives x<=m 3 Because the positive integer solution is , so 3<=m 3<4 (Note: Equal to 4 cannot be taken here, because it is equal to 4, then the positive integer solution can also be taken as 4, which does not meet the original conditions), and 9<=m<12, so the value range of m is [9,12).

Question 1: 32

Question 2: A<7

Question 3: x>0

Question 4: m<=9

3 Bury Song Meng 4-3 4=-3 2

2 Sakura Silver 3+4 5-27 5=-69 15

I don't know if it's right, you can do it yourself, after all, it's your own homework.

The following sentences are represented by an arithmetic equation that omits the plus sign:

1) The inverse of -8 and the sum of the reciprocal of -2.

2) The opposite of -6 is the sum of the number of 1 smaller than the opposite of 5.

3) -The difference between the opposite of the absolute value of one-third and the opposite number of four and two-thirds. -3 1- -4 and 3 2 = -3 1 3 14 = 3 13

4) A number smaller than -three-fourths.

4 3 -3/4 - 4 3 4 3 = 8 9

Write an equation.

It is then reduced to an algebraic formula with the plus sign omitted.

Write counts. Write the following equations first as addition-only equations, then in the form of sums with plus signs omitted, and also write the number of things that are blind (note: —is a minus sign. - is a minus)

3) (+1/4) - (7 and 1/3) - (minus 2/3) - 4) (+2/3) - (

Cover Empty + (Note: -59/15.)

Fill in + (positive) or - (minus) in the following to make the results -12 Sorry, I'm home alone, I can't do it, I can only ask you for help.

I didn't mean to do so many questions for you, I'll be sure to pay attention next time.

If it is positive I will count that the vertices of their seven corners are equally divided on the circumference, and the degrees of each angle (i.e., the circumferential angle) are: (360 7 2) degrees; Their sum is (360 7 2) degrees 7 = 180 degrees.

You're also 180 degrees This proves to be very complicated, and it's definitely not the first year of junior high school.

Analysis: a g is a total of seven angles, and the sum is the sum of the inner angles of the heptagonal type, which can be calculated by the formula 180*(n-2); Bring in n=7, the result is 900 degrees, and the key to solving the problem is to read the problem.

I can't see the diagram, but if it's a regular seven-pointed star, it should be the content of the first semester of junior high school, that is, you can connect one vertex of the seven-pointed star to other vertices, you can connect four lines, and divide the seven-pointed star into five triangles, and you know that the sum of the inner angles of each triangle is 180°

So the formula is.

∵(m+n)² 0

When (m+n) +2 takes the minimum value, m+n=0, that is, m,n are opposite numbers to each other, and the algebraic formula m -n = (m + n) (m-n) = 0 (m-n)=0;

The absolute values of two numbers that are opposite to each other are equal, |m|-|n|=0，2|m|-2|n|=0.

(m+n)2+2 takes the minimum value, then m+n=0, then m2+n2=(m+n)*(m-n)=0, because m=-n, the absolute value of m, the absolute value of n, then the absolute value of 2m—the absolute value of 2n, 0

Solution: m+n=0, m and n are opposite to each other, so m2-n 2=0,2|m|-2|n|=0

(m+n) 2+2 is the minimum value, i.e., (m+n) 2=0 is equal to the minimum value of 2

So m=-n. So m 2-n 2=m 2-(n) 2=0,2|m|-2|n|=0.

(-3a to the 2nd power) * (4a-3).

12a³+9a²

Three-quarters xy to the third power - 3xy) * one-third xy

1 4x y to the power of 4 x y - x y

Four-thirds ab) to the power of 2 * (-9/2a to the power of 2 b-12ab + three-quarters b to the 2nd power).

16 9a b * (9/2a to the 2nd power b-12ab + 3/4b to the 2nd power).

8a to the 4th power b -64 3a b + 4 3a b to the 4th power.

2A to the 2nd power* (1/2 ab + b to the 2nd power) - 5a* (2 power of a b-ab).

a³b-2a²b²-5a³b+5a²b²

6a³b+3a²b²

a(a-1)-a to the 2nd power.

a²-a-a²

a(-one-third xy + three-thirds y-2-2 -x) * 6xy).

- 3/3 xy + 3/2 y to the 2nd power - x to the 2nd power) *36x y to the 4th power.

12x y to the power of 5 + 48x y to the power of 6 - 36x to the power of 4 y to the power of y.

3m(2m+2n)+3m×2m

6m²+6mn+6m²

12m²+6mn

Typing is hard to do.

？。。Can it be converted into Arabic numerals?

The radius of the cylinder is 6 2 3, the base area is 3 9, then the volume of the cylinder is v 9 4 36;

The height of the cone is 7-4 3, the volume of the cone is v (1 3) 9 3 9, and the volume of the granary is 36 + 9 45

The volume of the lower cylinder: v cylinder = sh = r h= *(6 2) *4 = 36 The volume of the upper cone: v cone = 1 3 r h=1 3* *6 2) *7-4) = 1 3 *9*3 = 9

So the volume = 36 + 9 = 45

If you want, if you are an elementary school student, you can bring in = to find the approximate value. If you're in junior high school, that's fine.

Isn't it enough to just calculate the volume? 1 3x pi x radius squared x high + pi x radius squared x high, I haven't thought about it for a long time, or you will almost forget it.

3.Because "it is known that apples are 25 yuan per box, pears are 20 yuan per box, and grapes are 16 yuan per box." The total amount of money is 426 yuan, and the unit digit is "6", indicating that the number of boxes of grapes is "6, 10, 16 or 20 boxes", and only "16" matches the theme.

16 16 = 256 yuan, 426 256 = 170 yuan, and the number of boxes of apples may be "2 or 6 cases". If apples are 2 boxes, then pears are (170 25 2) 20 = 6 boxes. Three kinds of fruit are exactly 16 2 6 = 24 boxes.

If the apples are 6 boxes, then the pears are (170 25 6) 20 = 1 box, which does not fit the topic. So the unit bought 2 boxes of apples.

Let the amount of water flowing into the pond per hour be x, the amount of water pumped by 1 type A pump per hour is y, and the original water volume of the pond is a:

x+a=y1/3)x+a=(1/3)*2y

Beg? *x+a=3*？*y?

From the first two formulas, it can be deduced: a=y-x

y=2x so the third equation can be made as: (?) 1）x=?*6x?+1=6?

1 5 1 5 hours is 12 minutes 6The solution set from the inequality (2m-n)x+3m-4n 0 is x 4 9, and (2m-n)4 9 = 4n-3m and 2m-n<0, i.e., 8m-4n=36n-27m

35m=40n

n=7/8m

and 2m-n<0

Therefore, 2m<7 8m is m<0

Substituting n=7 8m into the inequality yields.

m-4*(7/8m)]x+2m-3*(7/8m)>0-5/2mx>5/8m

4mx>0

Because m<0 is -4m>0

So x>0

That is, the solution set of the inequality (m-4n) x+2m-3n>0 is Note: the above method is done according to the inequality (m-4n) x+2m-3n>0, if it is (m-4n)x+2m-3n<0, then the solution set is.

1. The addition of the two formulas can have mx+3x=10

That is, x*(m+3)=10, 10=1*10=2*5, when x is negative, m+3 is negative, so we are also negative, and if the conditions are not met, so x>0

When x=1, m=7

When x=2, m=2

When x = 5 and 10, m is negative.

So m=2 or 7

2. The equation 3kx+2y=6k-3 for x and y has the same solution for any value of k.

There are infinite solutions to the equation (3x-6) k+2y+3=0 for k, so 3x-6=0 and 2y+3=0

x=2，y=-3/23、

⒈ mx+2y=10 3x-2y=0；then (m+3)x=10;

m is a positive integer, i.e., (m+3)>3, then x>0;

It can be taken as m+3=5, x=2 or m+3=10, x=1

y=3 2x, m=2

3kx+2y=6k-3, that is, (3x-6)k+2y+3=0

Any value of k has the same solution, i.e., 3x-6=0;2y+3=0, then the solution x=2, y=-3 2

Set x boxes for apples, y boxes for pears, and boxes for grapes (24-x-y); x,y are integers.

The equation is: 25x+20y+16(24-x-y)=426;Simplification 9x+4y=42, for x, x can only take 2, then y=6, z=16

The unit purchased 2 boxes of apples.

Set up x 50 points and Y 20 points; x,y are integers.

50x+2 20y=350, i.e. 5x+4y=35;

Only x=3, y=5;3 should be added

Let the original water depth be a, the water inlet velocity is x, the pumping speed is y, and the time required is t;

then 60x+a=60y, 20x+a=2 20y, subtract, y=2x, substitution, a=60x;

and tx+a=3 ty, substitute y=2x, a=60x, and get t=12, that is, it takes 12 minutes.

solution(2m-n)x+3m-4n<0,x>(4n-3m) (2m-n);

Then (4n-3m) (2m-n)=4 9, simplified to m=8n 7, substituted by inequality (m-4n)x+2m-3n>0, that is, (8n 7-4n) x+16n 7-3n>0, and n<0, then reduce n, get x>-1 4

1. Add the two formulas to get (3+m)x=10

Arrays where two integers are multiplied by 10 are: 1 and 5, -1 and -10, -2 and -5

Since m is a positive integer, there is m>0,3+m>3, so we can know that 3+m=5, m=2 Second, we can know that the left and right sides are equal to k as unknowns, and there are: 3x=6, x=2;2y=-3, y=three,

-- It's a lot -- but it's all simple, leave it downstairs!

Or I'll do it-

Question 1: The preceding formula plus the posterior formula=> (m+3)x=10 , since m is a positive integer, and x is also, we can know that m=2, or m=7

Question 2: Assuming k is an unknown number, then the original formula is: (3x-6)k+2y+3=0, then =>x=2, y=

Question 3: From the end of the phone bill 6, it can be seen that the grapes are either 1 box, or 6 boxes, or 11 boxes, or 16 boxes or 21 boxes, and then suppose it is 1 box, then let the other 2 be x,y column equations, x+y=23, 25x+20y=410, no solution, then 6 boxes, x+y=18, 25x+20y=330, no solution, in the same way, when 11 boxes, no solution, 16 boxes, x=2, y=6, 21 boxes, no solution.

Question 4: If 20 points buy x cards and 50 points buy y cards, then 2x+x+y=18, 20x+20x+50y=350,=> y=3

Question 5: Let the water flow rate be x per hour, the pumping machine will pump y flow per hour, and there is a amount of water in the yuan pool.

a+x=y, a+1 3x=2*1 3y =>y=2a, x=a, then when using 3 units, a+a*t=3*2a*t =>t=12 minutes.

Question 6: The original formula is solved as: x>(4n-3m) (2m-n) and 2m-n<0 i.e. 4n-3m) (2m-n)=4 9 =>m=8 7n and m,n<0, in , bring in the following equation: x>(3n-2m) (m-4n)=, i.e. x>