Two junior high school math problems were in a hurry

1.Solution: Set up the original x people in the group, the time is t, and the total amount of the project is xtx+2) (t-2) = xt simplification: t-x-2 = 0 x-3) (t+6) = xt simplification: -t + 2x-6 = 0 + get: x=8

So t=x+2=10 (x+2)8=10x8x+16=10xx=8

2.It's too easy, will you do it?

1] Solution: Set up the original x people, it takes y days to complete.

x+2)(y-2)=xy

x-3)(y+6)=xy

2x+2y-4=0, i.e., x-y=-2

6x-3y-18=0, i.e. 2x-y=6

solution, x=8, y=10

Seeing that you are so anxious, I'll help you make one, but you have to understand it, this is a very basic engineering problem...

Set up a group of x people, originally planned to complete the project in y days, then according to the topic, with the same engineering quantity of the equation: (x+2)*(y-2)=(x-3)*(y+6) after sorting, the equation can be turned into: 8x-5y-14=0, that is, x=(5y+14) 8, according to the title, x, y are integers, and x>3, y>2, according to these conditions substituted integer, x=8, y=10....

Of course, if you continue to substitute, there may be other numbers that are appropriate, but limited to junior high school students, this can also be used as an answer... Another problem with a similar approach to the unknowns will also be derived...

1. Solution: If the original plan is to participate in tree planting, the actual number of people is from the topic

180/x—180/

Solution: x=30

So the actual number of people).

A: Actually, 45 people participated in the tree planting.

Second, there is a lack of conditions, and there is no telling what the daily output is when the price is 50 yuan.

1. If the actual number of participants is x, then the original planned number of participants is 2 3 x people, and the solution from the question is 180 x + 2=180 (2 3x) x=45

Question 2 (1) When the price per kilogram is 50 yuan. ( If the selling price per kilogram decreases or increases by one yuan.)

There should be another sentence in parentheses.

1. If the original number of participants is 2x, and the current number of participants is 3x, then 180 2x = 180 3x+2

If the solution is x=15, the actual number of participants is 45 people2

If it was originally planned that x people would participate in the tree planting activity, the actual number of people would be people.

180/x-180/

Solution: x=30

The second question seems to be missing a sentence.

Solution: Let the total number of people be x.

180/x -

270 - 180=3x

x=30A: So the actual number of participants is 30.

1.The actual number of participants is x.

180/x=180/(

x=302.Fewer conditions, when the price per kilogram is 50 yuan, how much is the sales volume?

1.If the remaining number is 3x-6 0, 6-3x 0, then the vertical head is 3x-6=0, x=2, y=8, and the answer is 6

2.x 0, y 0, be a god.

x-5（√xy）-6y＝0

x+√y）（√x-6√y）＝0

then x=6 y

x-2(√xy)+y]/[x+(√xy)-2y]=25y/40y=5/8

Plus or minus 6 according to the radical nature.

3x-6=6-3x=0 Find x and y.

1.{8a+5b>204...

3a+2b<80...

Left and right sides are left with -3 8, get -3a-15b 8< + get b 8 "then b<28

Substituting b<28 into , we get a<8

Multiply -5 2 by -15a 2-5b>-200....A 2>4 then a > 8

Substituting a>8 into , we get b>12

Because 8>a>8 there is no solution to the group of inequalities;

2.Looking at the picture, my answer is 72

Treat a as x and b as y

Draw the functions 8x+5y-204=0 and 3x+2y-80=0 on the Cartesian coordinate system, and move the terms yourself to become a function.

Then directly make the x of the left and right functions equal to y, and obtain a system of binary linear equations, and find x=8 and y=28

So their intersection is left marked with (8,28).

The part where 8x+5y-204 is greater than 0 is to the right of the line 8x+5y-204=0.

The part where 3x+2y-80 is less than 0 is to the left of the function line 3x+2y-80=0.

The part where they coincide is the black part to the right of the intersection.

So x>8, y<28

2..Let the length be x, the width y, and the diagonal length c

From the inequality x 2 + y 2 2xy, we can see that the minimum value of xy is (1 2) (x 2 + y 2) = (1 2) c 2

The circles should be arranged so that the diagonal length is the shortest.

Since x+y>c, the two circles are inscribed circles.

So when the diameters of both circles are on the diagonal, c is the shortest.

So c=10

So the minimum area is 50

Let n 2-n = x

Then the original becomes (x+1)(x+3)+1

x^2+4x+3+1

x^2+4x+4

x+2)^2

n^2-n+2)^2

When n is a natural number, (n 2-n + 1) (n 2-n + 3) + 1 is the perfect square.

1:x^3+2x^2+2006=(x^3+x^2-x)+(x^2+x-1)+2007=x(x^2+x-1)+(x^2+x-1)+2007=2007

2:(n^2-n+1)(n^2-n+3）+1=(n^2-n+1)(n^2-n+1）+2(n^2-n+1)+1

Treat (n 2-n+1) as a whole, so that t=(n 2-n+1) is equal to t 2+2t+1

1.x 2+x-1=0 gives x 2=1-x, and x 2+x=1;

x^3+2x^2+2006

x^2(x+2)+2006

1-x)(x+2)+2006

x-1)(x+2)+2006

x^2+x-2)+2006

2.Let n 2-n = x, then the original formula = (x+1)(x+3)+1x 2+4x+4

x+2)^2