Factor completely: 4u^3 + 16u^2 - 20u.
A4u(u+1)(u-5)
B4u(u-2)(u+10)
C4u(u-1)(u+5)
D2u(u-1)(u+10)
Answer & Solution
Correct answer: C. 4u(u-1)(u+5)
1. Factor out the GCF first: 4u cubed + 16u squared - 20u has a common factor of 4u, giving 4u(u squared + 4u - 5).
2. Inside the parentheses, find two numbers that multiply to -5 and add to 4.
3. The pair -1 and 5 multiplies to -5 and adds to 4.
4. Use -1 and 5 as the last terms to get 4u(u - 1)(u + 5), and check: 4u times (u squared + 4u - 5) gives back 4u cubed + 16u squared - 20u.
_Source: OpenStax Elementary Algebra (CC BY 4.0), Ch 7 "Factoring", section 7.3 Factor Quadratic Trinomials with Leading Coefficient Other than 1_
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