Question

Find trinomial (quadratic expression), given below, find whether it is factorisable or not. Factorise, if possible.
2x² - 7x - 15

Answer 1

Given expression : 2x² - 7x - 15
Comparing with ax² + bx + c, we get a = 2, b = -7, and c = -15
∴ b² - 4ac = (-7)² - 4(2)(-15) = 49 + 120 = 169, which is a perfect square.
∴ 2x² - 7x - 15 is factorisable.
Now, 2x² - 7x - 15
= 2x2 - 10x + 3x - 15
= 2x( x - 5 ) + 3( x - 5 ) 
= ( 2x + 3 )( x - 5 )