Question 190277
{{{(4 - i)*(4 + i)}}} Start with the given expression.



{{{(4)(4)+(4)(i)+(-i)(4)+(-i)(i)}}} FOIL.



{{{16+4i-4i-i^2}}} Multiply.



{{{16+4i-4i-1(-1)}}} Replace {{{i^2}}} with {{{-1}}}. Note: {{{i^2=-1}}}.



{{{16+4i-4i+1}}} Multiply.



{{{17}}} Combine like terms.



So {{{(4 - i)*(4 + i)=17}}}.