Question #27e2b

3 Answers
Feb 5, 2018

z1z2=2+i

Explanation:

We need to calculate
z1z2=43i12i

We can't really do much because the denominator has two terms in it, but there is a trick we can use. If we multiply the top and bottom by the conjugate, we'll get an entirely real number on the bottom, which will let us calculate the fraction.

43i12i=(43i)(1+2i)(12i)(1+2i)=4+8i3i+61+4=

=10+5i5=2+i

So, our answer is 2+i

Feb 5, 2018

The answer is =2+i

Explanation:

The complex numbers are

z1=43i

z2=12i

z1z2=43i12i

i2=1

Multiply the numerator and denominator by the conjugate of the denominator

z1z2=z1¯z2z2¯z2=(43i)(1+2i)(12i)(1+2i)

=4+5i6i214i2

=10+5i5

=2+i

Feb 5, 2018

2+i

Explanation:

z1z2=43i12i

multiply numerator/denominator by the complex conjugate of the denominator

the conjugate of 12i is 1+2i

Reminderxi2=(1)2=1

(43i)(1+2i)(12i)(1+2i)

expand factors using FOIL

=4+5i6i214i2

=10+5i5=2+i