Question 176897
The easy answer is {{{5/(7-4i)}}}.
Teacher's typically don't like complex numbers in the denominator.
So multiply numerator and denominator by the complex conjugate,
{{{(5/(7-4i))((7+4i)/(7+4i))=(35+20i)/(49+28i-28i-16i^2)}}}
{{{(5/(7-4i))((7+4i)/(7+4i))=(35+20i)/(49+16)}}}
{{{(5/(7-4i))((7+4i)/(7+4i))=(35+20i)/(65)}}}
{{{(5/(7-4i))((7+4i)/(7+4i))=(7/13)+(4/13)i}}}
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The reciprocal of (7-4i)/5 is (7/13)+(4/13)i.