Hi there!
First we need to remember the following.

Now substitute both of the formulas.

Work out the parenthesis.

And finally collect terms.

~ Hope this helps you!
Answer:
21
Step-by-step explanation:
f(x) = 2x^2 - x
f(-3) = 2*(-3)^2 - (-3)
=2*9 +3
=18 +3
=21
25-16=9
9+23=32
He had 32 CDs to begin with
Answer:
5.83 or E
Step-by-step explanation:
Use Pythagorean theorem. 5^2+3^2=c^2 because the diameter is perpendicular it cuts the chord in half.
25+9=c^2
34=c^2
5.83