Q3 of 227 Page 89

Find the GCD of the following pairs of polynomials using division algorithm.

3x3 + 18x2 + 33x + 18, 3x2 + 13x + 10

According to the question,


3x3 + 18x2 + 33x + 18 then put x = – 1 in that equation


put x = – 1


then, – 3 + 18 – 33 + 18 = 0


Then the equation is divisible by x + 1, using division algorithm method.


(x + 1)(3x2 + 15x + 18) = (x + 1)[3x2 + 9x + 6x + 18]


= (x + 1)[3x(x + 3) + 6(x + 3)]


= 3(x + 1)(x + 2)(x + 3)


3x2 + 13x + 10 = 3x2 + 3x + 10x + 10 = 3x(x + 1) + 10(x + 1)


= (x + 1)(3x + 10)


Greatest common divisor = (x + 1)


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