Given:
p(x) = 2x³ + 3x² + ax + b when divided by x - 2 and x + 2 leaves the remainders 2 , - 2.
Find:
Value of a and b
Solution:
✯ g(x) = x - 2
⟹ 0 = x - 2 [ g(x) = 0 ]
⟹ x = 2
★ p(2) = 2(2)³ + 3(2)² + a(2) + b
⟹ - 2 = 2 * 8 + 3 * 4 + 2a + b
⟹ - 2 - 16 - 12 - 2a = b
⟹ - 30 - 2a = b -- equation (1)
Similarly,
✯ g(x) = x + 2
⟹ 0 = x + 2
⟹ x = - 2
★ p( - 2) = 2( - 2)³ + 3( - 2)² + a ( - 2) + b
Substitute the value of b from equation (1).
⟹ 2 = 2 * ( - 8) + 3 * 4 - 2a - 30 - 2a
⟹ 2a + 2a = - 16 + 12 - 2 - 30
⟹ 4a = - 24
⟹ a = - 24/4
⟹ a = - 6
Substitute the value of a in equation (1).
⟹ - 30 - 2( - 6) = b
⟹ - 30 + 12 = b
⟹ - 18 = b
Therefore,
a = - 6
b = - 18.
I hope it will help you.
Regards.