(Q15)Find the roots of the following quadratic equations, if they exist by the method of completing the square.

(iv) x2 + 5x = -6x

Answer:

The given quadratic equation is x2 + 5 = -6x

x2 + 6x = -5

(x)2 + 2.(x).3 = -5

Now L.H.S is of the form a2 + 2ab

where b = 3

Adding b2 = 32 on both sides we get

x2 + 2(x)(3) + 32 = -5 + 32

(x + )2=

∴ x + =±

x = ±- or --

= - or - are the roots of the given quadratic equation