Question

What is the value of the expression given below? (5+3i)-(5+3i)(5-5i)

Answer 1

-35 + 13i

Explanation:

`i=√(-1)\to i^2=-1\\\\(5+3i)-(5+3i)(5-5i)\qquad\text{distribute}\\\\=(5+3i)(1-(5-5i))=(5+3i)(1-5-(-5i))=(5+3i)(-4+5i)\\\\\text{use}\ FOIL:\ (a+b)(c+d)=ac+ad+bc+bd\\\\=(5)(-4)+(5)(5i)+(3i)(-4)+(3i)(5i)\\\\=-20+25i-12i+15i^2=-20+13i+15(-1)\\\\=-20+13i-15=-35+13i`