length of a rectangle is 7cent. less than 3x its width. its area is 20.ct what is dimensions

Question

need dimensions.

Answer 1

Width of rectangle(b ) = x  cent

Length of rectangle(l ) = 3x - 7

Area = l *b

x (3x - 7) = 20

3x^2 -7x = 20

3x^2 - 7x - 20 = 0

Compare it to quadratic form ax^2+bx+c = 0

a  = 3, b  = -7, c = -20.

Roots are x  = [-b ± √(b^2-4ac] / 2a

x = [7 ± √(49+240)] / 6

x  = [7 ± √289] / 6

x  = [7 ± 17] / 6

x  = 24/6 and x  = -10/6

x  = 4 and x  = -5/3.

Dimensions of rectangles are positive.

Width x  = 4cent

So lenghth is 3x - 7 = 3(4) - 7 = 5 cent.