How do you do these math problems?

1.(2n-1) n 2, you don't need to explain much, right? Hi me if you need it.

2.First row a

Second row A+2

Third row A+2+2

The nth row A+2 (N-1) (according to the known conditions, the law can be obtained) The twenty-second row can accommodate 22 + 2 * (22-1) = 64 people.

3.Set the price to be $x, and the current cost is $y.

Before the price reduction, 25% = (x-2) 2*100%, x = gross profit margin increased by 15%, that is, it became 40%.

40%=（y=

1. y=(2n-1)/n^2

2. y=a+2(n-1) 64

3.Calculate the selling price = 2 (1-25%) = y1 and then calculate the reduced cost = y1 * (1-25%-15%) = y2, and the final answer is 2-y2

1.(2n-1) n squared.

Platoon: A+2 (N-1) Platoon 22: 22 2 (22 1) 64 people.

3.Price: RMB.

Let the cost be x. Then:(

Solution: x approx

then decrease: 2 yuan.

<> Question 1 Knott's hand is the core of the conventional limit finding hole, the first question needs to simplify the function of finding the limit, and the fifth question needs to be applied to the theorem 2 of finding the limit.

lim(x->2) (x 2+5) (x 2-3)lim(x->1) (x 2-2x+1) (x 2-x)lim(x->1) (x-1) 2 [x(x-1)]lim(x-> field fight1) (x-1) x

lim (x-> burning calendar + ) 1-x-x 3) (x+x 3) numerator denominator while removing the spine search x 3

lim(x->+1/x^3-1/x^2-1)/(1/x^2+1)lim(x->1)[ 1/(1-x) -3/(1-x^3) ]lim(x->1)

lim(x->1) [1+x+x^2)-3]/[1-x)(1+x+x^2)]

lim(x->1) (x^2+x-2)/[1-x)(1+x+x^2)]

lim(x->1) (x+2)(x-1)/[1-x)(1+x+x^2)]

lim(x->1) -x+2)/(1+x+x^2)sinx|≤1 and lim(x->+1/x=0lim(x->+sinx/x =0

Relieve the limb and answer the wide ruler if it is prudent to judge.

1.Zhi Mingmin took over, got 9

2.About go to guess Pei X-1, A: 0

3.The ratio of the coefficient of the highest subterm is obtained as -1

1+x+x^2-3)/[1-x)(1+x+x^2)]-x+2)/(1+x+x^2)--1.

May I?

Crossing the point G to do GN perpendicular to BC, doing DM perpendicular to EG and extending the intersection of BC at point H

Over the point shout silver G do GN perpendicular to the vertical group BC, in do DM perpendicular to EG and extend the intersection BC in the residual infiltration orange point H

<> this question is more comprehensive, the question is the midpoint, the use of the midpoint to double the length of the midline, and then the spine is constructed into a hand-in-hand congruence, and the problem is easy to deal with after finding the congruence. The picture only writes the approximate process, and the specific process is complete by itself.

When there is a midpoint in the question, be sure to start with the middle point.

Detailed, complete, clear, process, RT shows ......There are so many ...... answersHope it helps you solve your problem.

The first of the second ** is to find the derivative of the composite function, first find the outer layer, then find the inner layer, and multiply the two results.

ans=2*f(x)*f'(x)

Question 2: Finding the derivative of the same variable on both sides is sufficient.

1）2 * x + 2 * y + 2 * x * y'-2 * y * y'= 2, simplification to y'

2) y' / y+sin(x)=y + x * y', simplified to y'

1.Let the grain stored in warehouse B be twice as much as the grain stored in warehouse A after x days, then (32+4x)*2=57+9x

The solution is x=72Let the net weight of this barrel of oil be x kg, then 2x 3 = 4 (56-x), and the solution is x = 48

3.If the slow train travels x kilometers per hour, then 3x+7+25=3*40-25 is solved to x=21

1.From the meaning of the title: a*a-b*b=13, then (a+b)*(a-b)=13, since a, b are integers, then (a+b) and (a-b) can only be integers, and 13 can only be a combination of 13*1, so there is a+b=13, a-b=1, and the solution is: a=7, b=6

2.The right side of the original equation gives x +ax+b=x -x-30, and the two sides of the equation are compared, since the corresponding coefficients must be equal to satisfy the equation, then a=-1, b=-30

3.Original formula = a - (b +2b+1) = a - (b+1) = (a + b + 1) (a - b-1).

1.Let the side length of the large square be aThe side length of the small square is b

According to the problem, we can get a -b = (a + b) (a -b) = 13 are all integers. and a b a=

2.from (x+5) (x-6).

x²-x-30.∴a=

3.Original = a - (b+1).

a+b+1)(a-b-1)

Landlord. Typing is tiring. Give it some hard work.

1.The speed of the train is about 1 10 of the speed of the airliner, and the ratio of the speed of the train to the speed of the airliner is 1 : 10.

2.Simplification ratio.

6=7：23.The ratio of the three inner angles in a triangular row is 2:

3:1, the degrees of the three inner angles of this triangle are (60 degrees) and (90 degrees).

Let the three angles be 2x, 3x, x, and the sum of the inner angles of the triangle is 180 degrees, so 2x+3x+x=180 degrees, x=30 degrees, and the three angles are 60 degrees, 90 degrees, and 30 degrees respectively.

Question 1: 1:10 There is no process to speak of, just understand.

Question 2: 7:2 3:(6 7)=3*7 6=7:2 (:and is a meaning, divided by a number is equal to multiplying by his reciprocal).

Question 3: 60°90°30° (the sum of the inner angles of the triangle is 180°, so it is 180 (2+3+1)*2,180 (2+3+1)*3,180 (2+3+1)*1).

Question 1:10

Question 3: 60 degrees, 30 degrees, 90 degrees.

The Chibi community has a circular stage with a radius of 6 meters, and due to the needs of the performance, the circumference of the stage is now widened by 1 meter. How many meters has the current stage area increased?

13* A square plastic plate, the circumference is 40 decimeters, Master Li wants to cut the largest circle from it, how many square meters is the area of this circle?

1. There are x red balls, y yellow balls, and z basketballs.

y=2/3x

z=2/3y+3

x-z=32

Solve the system of equations: x=63, y=42, z=31

Balls in the wooden box: x+y+z=136

2. There are x grams of alcohol in the bottle.

2 3x+20+1 4*(2 3x+20)+35=x, x=360

That is, there turned out to be 360 grams of alcohol in the bottle.

Suppose there are x red balls, 2x 3 yellow balls, and 2x 3 2 3 +3 = 4x 9+3

x-32=4x/9+3

The number of x=63 yellow balls is 63 2 3=42.

The number of blue balls is 42 2 3 + 3 = 31.

The total number is 63 + 42 + 31 = 136.

Question 1: Let the number of red balls be x and the number of blue balls be y, and the system of equations can be obtained: y=2 3x * 2 3+3x-y=32 can be solved: x= 63 y=31

Let the number of red balls be x, the number of yellow balls be y, and the number of blue balls be z2 3*x=y

2/3*y+3=z

z+32=x

x=63 y=42 z=31

x+y+z=136

It turned out that there were x grams of alcohol in the bottle.

x-(2/3*x+20)(1+1/4)=35x=330

1. The number of yellow balls is two-thirds of the red ball, the number of basketballs is 3 more than two-thirds of the yellow balls, and the number of blue balls is 3 more than 2 3 * 2 3 = 4 9 more than the red ball.

So there are (32+3) (1-4 9)=63 red balls.

There are 63*2 3=42 yellow balls.

There are 42*2 3+3=31 blue balls.

Therefore, the wooden box contains a total of 63 + 42 + 31 = 136 balls.

2. The first time you pour out two-thirds and 20 grams, the second time you are everywhere is a quarter of the first time, then the second time you pour out all 2 3 * 1 4 = 1 6 and 20 * 1 4 = 5 grams.

It turned out that there was alcohol in the bottle (35 + 5 + 20) (1-2 3-1 6) = 360 grams.