How do you simplify $(1-4i)(2+i)$ ?

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Answer 1 · 2018-04-07T02:54:02

$5-7i$

Keep in mind that $i^2=-1$ , and proceed, multiplying this with a method resembling FOIL:

$(1-4i)(2+i)=1+i-(4)(2)i-4i^2$

$1+i-8i-4i^2$

Combine the like terms in the middle.
$1-7i-4i^2$

$1-7i-(4*-1)=5-7i$

Answer 2 · 2018-04-07T02:56:58

$6-7i$

$(1-4i)(2+i) = 1times (2+i)-4i times (2+i)$
$qquad = 1 times 2+1 times i -4i times 2-4i times i$
$qquad = 2+i-8i-4i^2 = 2-7i+4 = 6-7i$

How do you simplify (1-4i)(2+i)(1-4i)(2+i)?