===========================================
Work Shown:
[tex](14-3i)(14+3i)\\\\x(14+3i) \ ... \text{ let } x = 14-3i\\\\14(x)+3i(x)\\\\14(14-3i)+3i(14-3i) \ ... \text{ plug in } x = 14-3i\\\\196-42i+42i-9i^2\\\\196-9i^2\\\\196-9(-1)\\\\196+9\\\\205[/tex]
Recall that [tex]i = \sqrt{-1}[/tex] is the imaginary unit. Squaring both sides gets us [tex]i^2 = -1[/tex]
You can verify the answer using a tool like WolframAlpha.
