Mathematics
Using the Remainder Theorem, factorise the expression 3x3 + 10x2 + x - 6. Hence, solve the equation 3x3 + 10x2 + x - 6 = 0.
Factorisation
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Answer
For x = -1, the value of 3x3 + 10x2 + x - 6,
= 3(-1)3 + 10(-1)2 + (-1) - 6
= 3(-1) + 10(1) - 7
= 10 - 10
= 0.
Hence, (x + 1) is the factor of 3x3 + 10x2 + x - 6.
On dividing 3x3 + 10x2 + x - 6 by (x + 1),
we get, quotient = 3x2 + 7x - 6
Factorising 3x2 + 7x - 6,
= 3x2 + 9x - 2x - 6
= 3x(x + 3) - 2(x + 3)
= (3x - 2)(x + 3).
∴ 3x2 + 7x - 6 = (3x - 2)(x + 3).
Hence, 3x3 + 10x2 + x - 6 = (x + 1)(3x - 2)(x + 3).
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