Find a and b in Linear Function

Find \( a \) and \( b \)

Question:

If

\[ f(x)=ax+b \]

where \(a\) and \(b\) are integers,

\[ f(-1)=-5 \]

and

\[ f(3)=3, \]

then \(a\) and \(b\) are equal to

(a) \(a=-3,\; b=-1\)
(b) \(a=2,\; b=-3\)
(c) \(a=0,\; b=2\)
(d) \(a=2,\; b=3\)

Solution:

Given,

\[ f(-1)=-a+b=-5 \]

and

\[ f(3)=3a+b=3 \]

Subtracting,

\[ 4a=8 \]

\[ a=2 \]

Putting in

\[ -a+b=-5 \]

\[ -2+b=-5 \]

\[ b=-3 \]

Therefore,

\[ \boxed{a=2,\; b=-3} \]

\[ \boxed{\text{Correct Answer: (b)}} \]

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