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a) m(x) = (x - 5)(3 + 2x) - x² + 25
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Open Brackets
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= (x × 3) + (x × 2x) + (-5 × 3) + (-5 × 2x) - x² + 25
= 3x + 2x² - 15 - 10x - x² + 25 (Bring like-terms together in descending power order)
= 2x² - x² + 3x - 10x - 15 + 25
= x² - 7x + 10
b) In x² - 7x + 10, -7 is the sum and + 10 is the product
- 2 + - 5 = -7
- 2 × -5 = 10
So the factor of x² - 7x +10 is:
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(x - 2)(x - 5)
Solving ( x - 2 )( x - 5 ) = 0
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x - 2 = 0 | x - 5 = 0
x = 2 | x = 5
