Answer
$-5+5i$
Work Step by Step
Note: the standard form of a complex number is $a+bi$ where $i = \sqrt -1$ and $a$ and $b$ are real numbers.
Note: $i^{2} = \sqrt -1\sqrt -1 = -1$
$5i(1+i)$
Expand out the complex number:
$5i(1+i) = 5i+ 5i^{2}$
As seen in the note above, $i^{2} = -1$, so substitute in $-1$.
$5i(1+i) = 5i+ 5(-1)$
Simplify:
$5i(1+i) = 5i-5$
Therefore, the complex number expressed in standard form is:
$5i(1+i) = -5+5i$
