Question

A rectangle has length (x+4) cm and width (x-3) cm. Its area is 30 square centimeters. Write a quadratic equation and solve it to find the length of the rectangle.

Answer 1

(x+4)(x-3)=30

x^2 +x -12 =30

x^2 +x =42

x^2 +x -42 =0

(i solved it by factorising: _x^2 × -42)

x^2 -6x +7x -42 =0

x(x-6) +7(x-6) 0

(x-6)(x+7)=0

x=6; x=-7

since it's a length, x can't be a negative number, so it must be 6