Question

How to do 21st question. Pls tell fast .

Answer 1

(21)

Given : (a + b + c)^2 - (a - b - c)^2 + 4b^2 - 4c^2

= > a^2 + b^2 + c^2 + 2ab + 2bc + 2ca - a^2 - b^2 - c^2 + 2ab - 2bc + 2ac + 4b^2 - 4c^2

= > 4b^2 + 4ab + 4ac - 4c^2

= > 4(b^2 + ab + ac - c^2)

= > 4(ab + b^2 - bc + ac + bc - c^2)

= > 4(b(a + b - c) + c(a + b - c))

= > 4(b + c)(a + b - c).

Hope this helps!