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If (x + 8) is a factor of f(x), which of the following must be true?
A) x = –8 and x = 8 are roots of f(x)
B) Neither x = –8 nor x = 8 is a root of f(x).
C) f(–8) = 0
D) f(8) = 0
On dividing two numbers, if we are getting remainder equal to zero then the smaller number will be the factor of the larger number.
Answer: Option C f(–8) = 0 is correct.
Let us proceed step by step to find the answer.
When we divide any polynomial by (x - a), we obtain a result of the form:
f (x) = (x - a) q (x) + f (a) [From Euclid's division algorithm]
If the remainder f (a) = 0, then (x − a) is a factor of f (x) --------(1)
Hence, from the given data in the question,
(x + 8) is a factor of f(x)
Therefore, f (-8) = 0 on substituting x = -8 [ from equation (1) ]
Thus, option C f(–8) = 0 is correct.