The HCF of the functions x3+(a+b)x2+(ab+1)x+b and x3+2ax2+(a2−1)x+a is
A
x2+ax+1
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B
x2+bx+1
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C
x2+x+a
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D
x2+x+b
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Solution
The correct option is Ax2+ax+1 x3 + (a +b)x2 + (ab + 1)x + b = x3 + (a +b)x2 + abx + x + b = x [x2 + (a + b)x + ab] + (x + b) = x (x + a) (x + b) + (x + b) = (x + b) [x (x + a) + 1] = (x + b) (x2 + ax + a)
x 3 + 2ax 2 + (a 2 + 1)x + a = x3 + 2ax2 + a 2 x + x + a = x (x 2 + 2ax + a 2 ) + (x + a) = x (x + a) (x + a) + (x + a) = (x + a) [x (x + a) + 1] = (x + a) (x 2 + ax + 1) Common factor between the two polynomials = x 2 + ax + 1 ∴ HCF = x 2 + ax +1