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

5-46i

Step-by-step explanation:

1. Multiply (10-4i) and (4-5i), I recomnd using foil:

40-50i-16+20i^2 + (-15+20i)

2. Remove the parenthesis around -15+20i

*we can do this since there is a "+":    

40-50i-16+20i^2 + (-15)+20

3. Simplify i^2

* i^2 is -1 by textbook defination:

40-50i-16+20(-1) + (-15)+20

4. Simplify

40-50i-16-20 + (-15)+20

6. Combine like terms:

-5-50i-16i+20i

5-46i

And the problem is done

i think it would be 42cm

the answer is two. hope this !