polynomials answerif X square + 2 X square + a x + b has factor X + 1 and x minus 1 then find a and b
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Given :-
x + 1 and x - 1 are the factors of polynomial x² + 2x² + ax + b = 3x² + ax + b
here, we've to find the value of a and b
when x = -1 (x + 1 as factor),
➡ p(-1) = 3(-1)² + a(-1) + b = 0
➡ -3 - a + b = 0
➡ -a + b - 3 = 0 -------(i)
when x = 1(x - 1 as factor),
➡ p(1) = 3(1)² + a(1) + b = 0
➡ 3 + a + b = 0
➡ a + b + 3 = 0 -------(ii)
subtracting equation (ii) from (i), we get
➡ (-a + b -3) - (a + b + 3) = 0
➡ -a + b - 3 - a - b - 3 = 0
➡ -2a - 6 = 0
➡ -2a = 6
➡ a = 6/-2
➡ a = -3
substituting a = -3 in equation (i),
➡ -(-3) + b - 3 = 0
➡ 3 + b = 3
➡ b = 3 - 3
➡ b = 0
hence, the value of a = -3 and b = 0
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