Question

please help me very important questions

Answer 1

$(a+b+c)^2=a^2+b^2+c^2+2(ab+bc+ac)$

plug in the terms and simplify

Answer 2

by use the identity
(a+b+c)^2 = a^2 + b^2 + c^2 + 2 (ab+ bc+ ca)
(-3a)^2 +4b^2+(-5c)^2+2 (-12ab-20bc+15ac)
now u try this question becauuusse

practice makes a man perfect