Simplify the following expression (10-4i) (4-5i) (-15+20 i)

Step-by-step explanation:

(10-4i) (4-5i) (-15+20i)

(10-4i) (4-5i) = 10*(4-5i) - 4i*(4-5i)

= 10*4 - 10*5i - 4i*4 + 4i*5i

= 40 - 50i - 16i + 20i² =40 - 66i + 20*-1   {i² =-1}

= 40 - 66i -20

= 20 - 66i

(20 - 66i) (-15 + 20i) = 20*(-15 + 20i)  - 66i*(-15 + 20i)

= -300 - 400i + 990i - 1320i²

= -300 - 400i + 990i - 1320* (-1)

= -300 - 400i + 990i + 1320

= 1020 + 590i

it's equivalent, so we can say that its equal.

let's call the denominator x and the numerador is 18 less then denominator, x - 18.

multiply

2.x = 5.(x - 18)

2x = 5x - 90

90 = 5x - 2x

90 = 3x

x = 90/3

x = 30

so:

answer

you start with $5 and save $10 a week until you have at least $45wer

step-by-step explanation: