(x+x+2)(x- 1)/2=8

x=3

Upper sole = 3cm, lower sole = 5cm and height = 2cm.

6. Set the width to xcm.

? 2*(5/2x *x +5/2x *5 + x*5) = 40

? x= 1

? Width = 1cm, length =2.5cm, height =5cm.

7. X teams should be invited to participate.

? x(x- 1)/2= 15

? X 1=6, x2=-5 (omitted)

? Six teams should be invited to participate.

8. Set the length x meters

x(20/2-x/2)=50

? x= 10

? Surround a rectangle with a length of 10m and a width of 5m.

9. Let x be the average interest rate cut each time.

? 1.98%( 1-x)^2=2.25%

? x= 0.066 = 6.6%

10. Let the annual growth rate be x.

? 12000( 1+x)^2= 14520

? x=0.208=20.8%

? The annual growth rate is 20.8%

1 1. Set the length to x meters.

x(40/2-x)=75

? x 1=5，？ x2= 15

Enclose a rectangle with a length of 15m and a width of 5m.

? x(40/2-x)= 10 1

? x^2-20x+ 10 1=0

? delta = 400-404 =-4 & lt； 0

? This equation has no real root.

? So I can't surround it.