SOLUTION: x3+3x2+5x+15

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Question 714726: x3+3x2+5x+15
Answer by DrBeeee(684) About Me  (Show Source):
You can put this solution on YOUR website!
Given:
(1) x%5E3+%2B+3x%5E2+%2B+5x+%2B+15
Now factor x%5E2 out of the first two terms and 5 out of the third and fourth terms to get
(2) x%5E2%2A%28x%2B3%29+%2B+5%28x%2B3%29
Now factor (x+3) out of (2) and get
(3) %28x%2B3%29%2A%28x%5E2%2B5%29
Set (3) equal to zero gives us the three roots
(4) x = (-3,+isqrt%285%29,-isqrt%285%29)