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If \( \Large f \left(x\right)=ax+b,\ f \left(1\right)=-2,\ and\ f \left(2\right)=6,\ then\ f \left(3\right)\) is equal to:

A) -24
B) -12
C) 12
D) 14

Correct Answer:




D) 14

Description for Correct answer:
Since \( \Large f \left(x\right)=ax+b, \)

Therefore, \( \Large f \left(1\right)=-2,\ or\ a+b=-2 \)

and \( \Large f \left(2\right)=6,\ or\ 2a+b=6 \)

Solving (i) and (ii), we get

a = 8 and b = -10

Therefore, \( \Large f \left(x\right)=8x-10 \)

Hence, \( \Large f \left(3\right)=8 \times 3 -10 = 14 \)

Part of solved Rational expression questions and answers : >> Elementary Mathematics >> Rational expression

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