Solve: (m²-m) (m²-m-7) = -6
Answers
Taking m² - m as x,
(m² - m) (m² - m - 7) = - 6
⇒ x (x - 7) = - 6
⇒ x² - 7x = - 6
⇒ x² - 7x + 6 = 0
⇒ x² - x - 6x + 6 = 0
⇒ x(x - 1) - 6(x - 1) = 0
⇒ (x - 6)(x - 1) = 0
∴ x = 6 OR x = 1
⇒ m² - m = 6 OR m² - m = 1
If m² - m = 6,...
m² - m = 6
⇒ m² - m - 6 = 0
⇒ m² + 2m - 3m - 6 = 0
⇒ m(m + 2) - 3(m + 2) = 0
⇒ (m - 3)(m + 2) = 0
∴ m = 3 OR m = -2
If m² - m = 1,...
m² - m = 1
⇒ m² - m + 0.25 = 1 + 0.25
⇒ (m - 0.5)² = 1.25
⇒ m - 0.5 = ±√1.25
⇒ m - 0.5 = ± 0.5√5
⇒ m = 0.5 ± 0.5√5
⇒ m = (1 ± √5) / 2
So there are 4 values for m.
1. m = 3
2. m = -2
3. m = (1 + √5) / 2
4. m = (1 - √5) / 2
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I was not able to split the middle term of m^2 - m - 1 = 0, so I used the 'completing the square' method.