Question

Add or subtract. Write the result in the form a+bi

Answer 1

Number 1: (-1+2i)+(6-9i)

$Group\:the\:real\:part\:and\:the\:imaginary\:part\:of\:the\:complex\:number\\\left(a+bi\right)\pm \left(c+di\right)=\left(a\:\pm \:c\right)+\left(b\:\pm \:d\right)i\\=\left(-1+6\right)+\left(2-9\right)i\\=5-7i$

Number 2: (3-3i)-(4+7i)

$Group\:the\:real\:part\:and\:the\:imaginary\:part\:of\:the\:complex\:number\\\left(a+bi\right)\pm \left(c+di\right)=\left(a\:\pm \:c\right)+\left(b\:\pm \:d\right)i\\=\left(3-4\right)+\left(-3-7\right)i\\Refine\\=-1-10i$

Number 3: (-5+2i)+(-2+8i)

$Group\:the\:real\:part\:and\:the\:imaginary\:part\:of\:the\:complex\:number\\\left(a+bi\right)\pm \left(c+di\right)=\left(a\:\pm \:c\right)+\left(b\:\pm \:d\right)i\\=\left(-5-2\right)+\left(2+8\right)i\\Refine\\=-7+10i$