warm-up multiply complex numbers write the expression as a complex number in standard form. 1....
TRANSCRIPT
Warm-Up Multiply complex numbers
Write the expression as a complex number in standardform.
1. 4i(–6 + i) 2. (9 – 2i)(–4 + 7i)
SOLUTION
1. 4i(–6 + i) = –24i + 4i2 Distributive property
= –24i + 4(–1) Use i2 = –1.
= –24i – 4 Simplify.
= –4 – 24i Write in standard form.
Warm-Up Multiply complex numbers
2. (9 – 2i)(–4 + 7i)
Multiply using FOIL.= –36 + 63i + 8i – 14i2
= –36 + 71i – 14(–1) Simplify and use i2 = – 1 .
= –36 + 71i + 14 Simplify.
= –22 + 71i Write in standard form.
How to… Divide complex numbers
Remember when we needed to divide radical expressions in Math 1??
How did we do that?!?!
As a refresher, how would you divide the following:
4
2 + √3. 2 - √3
2 - √3=
8 - 4√3
4 - 3=
8 - 4√3= 8 - 4√3
1
The conjugate of 2 + √3!
How to… Divide complex numbers
Multiply the numerator & denominator by the conjugate!
Then complete your steps for multiplying complex numbers!
(a + bi) has a conjugate of (a – bi)
and
(a – bi) has a conjugate of (a + bi)
Goal NO IMAGINARY NUMBERS IN THE DENOMINATOR!!
How to… Divide complex numbers
i = √-1
i ² = -1
i ² CANNOT be in the simplified answer!
Example #1 Divide complex numbers
Write the quotient in standard form.
7 + 5i 1 4i
7 + 5i 1 – 4i
7 + 5i 1 – 4i= 1 + 4i
1 + 4i Multiply numerator and denominator by 1 + 4i, the complex conjugate of 1 – 4i.
7 + 28i + 5i + 20i2
1 + 4i – 4i – 16i2= Multiply using FOIL.
7 + 33i + 20(–1)1 – 16(–1)= Simplify and use i2 = 1.
–13 + 33i 17= Simplify.
Example #1 Divide complex numbers
1317 –= + 33
17 i Write in standard form.
GUIDED PRACTICE
1.
1 + 9i
i(9 – i)
2. (3 + i)(5 – i)
16 + 2i
3. 5 1 + i
52 – 5
2 i
1113 + 16
13 i
4. 5 + 2i 3 – 2i
Write the expression as a complex number in standard form.
ANSWER
ANSWER ANSWER
ANSWER