Question

15.Calcule
a) (-12).(-30)
b) (-28):(+7)​

Answer 1

As respostas são:

A +360

B -4

Answer 2

caso tenha problemas para visualizar a resposta experimente abrir pelo navegador https://brainly.com.br/tarefa/32649369

$\boxed{\tt{\underline{Regra~de~sinais~para~multiplicac_{\!\!,}\tilde{a}o~e~divis\tilde{a}o}}}\\\boxed{\begin{array}{c}\sf{+\cdot +=+}\\\sf{-\cdot-=+}\\\sf{+\cdot-=-}\\\sf{-\cdot+=-}\end{array}}\\\boxed{\begin{array}{c}\sf{+\div+=+}\\\sf{-\div-=+}\\\sf{+\div-=-}\\\sf{-\div+=-}\end{array}}$

$\tt{a)}~\boxed{\boxed{\boxed{\boxed{\sf{(-12)\cdot(-30)=+360}}}}}\\\tt{b)}~\boxed{\boxed{\boxed{\boxed{\sf{(-28)\div(+7)=-4}}}}}$