Question

How do you simplify (-4i)(7i)?

Answer 1

For this case we must simplify the following expression:

`(-4i) (7i)`

We have to by definition that:

`- * + = -\\- * - = +\\i ^ 2 = -1`

So:

`-4i * 7i = -28i ^ 2 = -28 (-1) = 28`

Finally we have that the expression is equivalent to:

`(-4i) (7i) = 28`

Answer:

`(-4i) (7i) = 28`

Answer 2

`\bf (-4i)(7i)\implies -28i^2\implies \stackrel{\textit{recall that }i^2 = -1}{-28(-1)}\implies 28`