Question

factorise:(3a-7b-c)²​

Answer 1

Question =》(3a-7b-c)²

Using the identity (a+b+c)²=a²+b²+c²+2ab +2bc+2ca

Solution =》(3a-7b-c)²

=(3a)²+(7b)²+c²+2×3a×7b+2×7b×c+2×c×3a

=9a²+49b²+c²+42ab+14bc+6ca

Answer 2

Step-by-step explanation:

Using the identity,

(a+b+c)² = a²+b²+c²+2ab+2bc+2ac

Now, put the value on the formula and execute...

⇒(3a-7b-c)²= (3a)²+(-7b)²+(-c)²+2.3a(-7b)+2.(-7b)(-c)+2.3b.(-c)

⇒(3a-7b-c)² = 9a²+49b²+c²-42ab+14bc-6ac