In a rectangle, the length is twice as long as the width.if its length and width are both increases by 6 cm, it's area is increased by 162 cm. Find its original dimensions.

Respuesta :

original width = x
original length = 2x
original area = x * 2x = 2x²

increased width = x+6
increased length = 2x+6

(x+6)(2x+6) = 2x² + 162
2x² + 6x + 12x + 36 = 2x² + 162
2x² - 2x² + 18x = 162 - 36
18x = 126
x = 126/18
x = 7 cm  ←  original width 

original length = 2x = 2 * 7 = 14 cm