Question

expand
(3а - 5b-7с)^2​

Answer 1

Answer:

you put the formula

${(a + b + c)}^{2} = {a}^{2} + {b}^{2} + {c}^{2} + 2ab +2 bc + 2ca$

then get the answer

Answer 2

Answer:

(3а - 5b-7с)^2

$=( 3a) {}^{2} + ( - 5b) {}^{2} + ( - 7c ) {}^{2} + 2(3a)( - 5b)+ 2( - 5b)( - 7c) + 2( - 7c)(3a) \\ = 9a {}^{2} + 25b {}^{2} + 49c {}^{2} - 30ab + 70bc - 42ac$