Junior 1 math problems good plus points!!! ）

1) Absolute value = 0

3a-b+1=0 and 2a+3b-25=0

Solving the unary quadratic inequality yields a=2, b=7

Substituting inequalities, 4x-7(x-7)>19. The second inequality is wrong. Why didn't b....

Anyway, you can bring it in and solve it yourself.

2) s positive = 25

s three = 18 * h * 1 2 = 9 h

That is, the solution is 0<9h<=25 (remember to be greater than 0!) I don't know how many times I got wrong when I was in junior high school! Then do the math yourself.

If there is anything you don't understand, ask again.

Why can't you understand your supplement = =;

1.Since the absolute value can only be greater than or equal to 0, the addition of the two equations =0 gives a=2 and b=7

After substitution, x belongs to (1, 3, 10), that is, 1 3 is less than x, less than 10, less than or equal to 5 2

h less than or equal to 25 9

The absolute value is greater than or equal to 0

So the addition will not be less than 0

So plus equals 0

If one is greater than 0, the other is less than 0 and is not true.

So both are equal to 0

So 3a-b+1=0

2a+3b-25=0

a=2,b=7

So. 4x-7(x-7)>19

4x+49>19

4x<30

x<15/2

x+(3-7)>6

x>10

So 10 is not true. So there is no solution.

1 solution: Set the original plan for each person to stack x thousand paper cranes.

Then: 40x=(40-10)*(x+8).

40x=30x+240

10x=240

x=24A: This class was originally scheduled to stack 24 paper cranes per person.

2 solution: Let the average speed from Beijing to Wuhan be x kilometers per hour: 15x=8x+(7-4)*(2x+50)15x=8x+3*(2x+50).

15x=8x+6x+150

15x=14x+150

x=150A: The average speed from Beijing to Wuhan is 150 kilometers per hour: The average speed from Wuhan to Guangzhou after the speed increase is: 2*150+50=300+50=350

x=30(8+x)

10x＝240

x 242, set the average speed from Beijing to Wuhan is x

15x＝8x＋3（2x＋50）

The solution is x=150

The average speed from Wuhan to Guangzhou is 2x 50 150 2 50 350

The first one is a b and subtract an equal trillion of liquid, and the equation remains the same.

The second x is equal to 0 when the sum of a number is equal to 0, then the two numbers must be equal in magnitude and value, and the sign is opposite.

The third can be thought of as -8*x=4 x is the multiplier, and the multiplier = product divided by another multiplier equals 4 divided by -8 equals -1 2

The fourth 1 3 * x=-2 x=-2 divided by 1 3=-2*3=6

1: Add 5 on both sides

2: Subtract 5 from both sides

3: Divide by -8 on both sides

4: Multiply both sides by 3