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Factorise the following polynomials: x3+13x2+31x-45,given that (x+9) is a factor |
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Answer» X^3 +13x^2 + 31X - 45 = x^3 - x^2 + 14x^2 - 14x + 45X - 45 = x^2 ( x - 1) + 14x (x - 1) + 45 (x - 1) = (x - 1)(x^2 + 14x + 45) = (x-1) [x^2 + 5X + 9x + 45] = (x-1)[ x(x +5) + 9 (x +5)] = (x-1)(x+5)(x+9) |
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