I forgot but I used to know this one
Answer:
A graph shows zeros to be ±3. Factoring those out leaves the quadratic
(x-2)² +1
which has complex roots 2±i.
The function has roots -3, 3, 2-i, 2+i.
Step-by-step explanation:
Same strategy as before: transform <em>X</em> ∼ Normal(76.0, 12.5) to <em>Z</em> ∼ Normal(0, 1) via
<em>Z</em> = (<em>X</em> - <em>µ</em>) / <em>σ</em> ↔ <em>X</em> = <em>µ</em> + <em>σ</em> <em>Z</em>
where <em>µ</em> is the mean and <em>σ</em> is the standard deviation of <em>X</em>.
P(<em>X</em> < 79) = P((<em>X</em> - 76.0) / 12.5 < (79 - 76.0) / 12.5)
… = P(<em>Z</em> < 0.24)
… ≈ 0.5948
1.50x + 450 = 3x
450 = 3x - 1.50x
450 = 1.50x
450/1.50 = x
300 = x
300 copies must be sold to break even
