Question

Find roots of quadratic equations xsquare+4x-5=0 by completing square method.

Answer 1

x²-4x+5=0

1) half the coefficient of x square, add and subtract to balance

x²−4x+2²+5−2²=0

2) so terms form a perfect square

(x−2)²+5−4=0

(x−2)²+1=0

3) solve for x

(x−2)²=−1

x−2=±√−1

x−2=±i

∴x=2±i