^{2}

^{2}=-1 substitute and group like terms then simplify

(4+20i) and (4-5i)

Tutors, sign in to answer this question.

PAT T. | Every problem has a solution let's find it.Every problem has a solution let's find ...

use the distributive property

(4 + 20i)(4-5i)= 4(4-5i) + 20i(4-5i)

get rid of parenthesis

16 -20i + 80i -100i^{2}

i^{2}=-1 substitute and group like terms then simplify

16 + -100(-1) + i(-20 + 80)

116 + 60i

(4+20i) x (4-5i)

factor out the 4 out

4( 1+5i) (4-5i)

multiply all the parts together

[4]x[1x4 + 1x(-5i) +(5i)x4 + (5i)(-5i)]

You multiply complex numbers similar to the way toy multiply binomials.

=[4]x[ 4 - 5i + 20i -25]

= 4(29+15i)

Already have an account? Log in

By signing up, I agree to Wyzant’s terms of use and privacy policy.

Or

To present the tutors that are the best fit for you, we’ll need your ZIP code.

Your Facebook email address is associated with a Wyzant tutor account. Please use a different email address to create a new student account.

Good news! It looks like you already have an account registered with the email address **you provided**.

It looks like this is your first time here. Welcome!

To present the tutors that are the best fit for you, we’ll need your ZIP code.

Please try again, our system had a problem processing your request.

Laura M.

Graduate Student Experienced in Tutoring Variety of Subjects

$11.25 per 15 min

View Profile >

Randee S.

Dynamic, versatile tutor for core subject areas K-12

$8.75 per 15 min

View Profile >

Haroldo S.

Biomedical Engineer (UC Berkeley PhD) for Math and Science Tutoring

$12.50 per 15 min

View Profile >