Question

Show that: (6a – 3b) 2 + 72ab = (6a + 3b)2

Answer 1

Answer:

Correct option is

B

36a

2

+36ab+9b

2

(6a+3b)

2

=(6a)

2

+(3b)

2

+2×6a×3b

=36a

2

+9b

2

+36ab

Hence, Option B is correct.

Answer 2

Information to prove :

(6a – 3b)² + 72ab = (6a + 3b)²

RHS :

(6a – 3b)²

= 36a² – 2.6.3.ab – 9b² + 2.36ab [this is the 'completing the square' method]

= (6a – 3b)² + 72ab

LHS :

(6a – 3b)²

LHS = RHS [ hence proved ]