if (x-2)(x-4) are the factors of x³-ax²+14x+b then find values of a and b
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Answers
Answer:
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(x-2) and (x-4) are the factor of x³ - ax² + 14x + b
now find the value of a and b
to find first equation we know that
divider is (x-2)and dividend is x³ - ax² + 14x + b
so put (x-2) equal to zero
x-2 = 0
x=2
now put the value of x in the dividend
P(2) = 2³ - a×2² + 14×2 + b
= 8 - 4a + 28 + b
so
4a-b = 8 + 28
4a-b = 36 this is equation 1
now find equation 2
the divider is now (x-4)
so put (x-4) equal to zero
(x-4) = 0
x=4
now put the value of x in dividend
P(4) = 4³ - a×4² + 14×4 + b
= 64 - 16a + 56 + b
so
16a-b = 64 + 56
16a-b = 120 this is equation 2
now subtract equation 1 from equation 2
16a-b = 120
- 4a + b = -36 ( sign change because we subtract the equation)
so the value of a from the solving of equations is
12a = 84
a = 7
now we found the value of a
now we have to find the value of B
put the value of a in equation 1
4a - b = 36
4×7-b = 36
28 - b = 36
-b = 8
so
b = - 8
Verify the answer
4×7 - (-8) = 36 equation 1 verified
16×7 - (-8) = 120 equation 2 verified
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