Question

Factorise the following step by step
a) 9x²-24xy+16y²
b) x²+9x+20

Answer 1

Answer:

a)(9x²-24xy+16y²)

={(a+b)²=a²+b²+2ab}

=(3x-4y)²

b)x2+9x+20

first multiply the coefficient of x2 and constant=20×1=20

multiplication should be 20 and sum should be the coefficient of x =9

sum=9

multiplication=20

both conditions satisfy only when the numbers are 4 and 5

x2+4x+5x+20

x(x+4)+5(x+4)

(x+4)(x+5)

x=-4

x=-5

therefore we factorised and found out the values of x=-4,-5