Question

3a^2- b^2 ( para a = -2 e b = - 7)

Answer 1

$3 {a}^{2} - {b}^{2} = 3 \times {( - 2)}^{2} - { ( - 7)}^{2} = \\ = 3 \times 4 - 49 = 12 - 49 = 37$

Answer 2

$3a^2-b^2=~~~~para~~a=-2 ~~~e~~~b=-7\\ \\ 3(-2)^2-(-7)^2=\\ \\ 3(+4)-(+49)=\\ \\ +12-49=-37$