SOLUTION: the lower base of a trapezoid is x+7 cm and the upper base is x+4 cm. if the distance between them is x cm and the area of the trapezoid is 20 sq. cm, find x

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Question 571507: the lower base of a trapezoid is x+7 cm and the upper base is x+4 cm. if the distance between them is x cm and the area of the trapezoid is 20 sq. cm, find x
Answer by mananth(16946) About Me  (Show Source):
You can put this solution on YOUR website!
The area of a trapezoid is = 1/2 the sum of parallel sides * the height
Area = %281%2F2%29%2A%28x%2B4%2Bx%2B7%29%2Ax

Simplify
(x^2+11x)/2 = 20
2x^2+11x=40
2x^2+11x-40=0
2x^2+16x-5x-40=0
2x(x+8)-5(x+6)=0
(2x+6)(x-5)=0
2x+6 =0
2x=-6
x=-3
OR
x=5