The area of a rectangle is given by the expression 3x^2+7x-40.

Question

A. What is the length of the rectangle if its width is x+5?

B. If x=2cm, find the length, width and area of the rectangle?

Answer 1

A.

W = x + 5

A = W ∙ L

3 x² + 7 x - 40 = ( x + 5 ) ∙ L

L = ( 3 x² + 7 x - 40 ) / ( x + 5 )

L = 3 x - 8

Question B does not make sense.

When x = 2

A = 3 x² + 7 x - 40 = 3 ∙ 2² + 7∙ 2 - 40 = 3 ∙ 4 + 14 - 40 = 12 + 14 - 40 = -14

If area is negative, length or width must be negative.

It is impossible.