(20 + 15 i)(15i - 20) =
(Type your answer in the form a + bi.)

answer

-625

foil

first foil (20 + 15i)(15i - 20) to get

(20 * 15i) + (20 * (-20)) + (15i * 15i) + (15i * (-20))

= (300i) + (-400) + (225) + (-300i)

combine like terms

combine the i terms together to get

(300i) + (-400) + (225) + (-300i)

300i - 400 + 225 - 300i

= -400 + 225

substitute -1 into i^2

remember that i = so = -1, and substitute this into -400 + 225i^2

-400 + 225i^2

= -400 + 225(-1)

= -400 -225

= -625

the answer is b: 18

step-by-step explanation:

use the pythagorean theorem to .

a^2+b^2=c^2

plug 18 for "r"

the 2 legs are 18 and 24

18^2+24^2=c^2

324+576=c^2

900=c^2

c=30

30-12=18

18 is the radius

: )