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3 Answers
- PuzzlingLv 71 month ago
Let u = cos x:
Factor:
6u² - 13u - 5
Method:
Multiply the outer coefficients --> 6 * -5 = -30
Think of two numbers that multiply to be -30 but add to be -13
Answer:
-15 * 2 = -30
-15 + 2 = -13
Split the middle term into -15u and 2u:
6u² - 15u + 2u - 5
Factor each pair:
3u(2u - 5) + 1(2u - 5)
(3u + 1)(2u - 5)
Substitute back:
(3 cos x + 1)(2 cos x - 5)
- JohnathanLv 71 month ago
6 cos^2(x) - 13 cos(x) - 5
= 6 cos^2(x) - 15 cos(x) + 2 cos(x) - 5
= 3 cos(x)(2 cos(x) - 5) + 2 cos(x) - 5
= (3 cos(x) + 1)(2 cos(x) - 5). Final.
Just simple FOIL.
