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If $f(x)=a x^{2}+b x+2$ and $f(1)=4, f(3)=38$, then $a-b=$
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2086 Upvotes
Verified Answer
The correct answer is:
8
$$
\begin{array}{l}
f(1)=4 ; \quad a+b=2...(1) \\
f(3)=38 ; \quad 9 a+3 b+2=38-\text { (2) } \\
3 a+b=12
\end{array}
$$
Solving (1) \& (2)
$$
\begin{array}{l}
a=5, b=-3 \\
a-b=8
\end{array}
$$
\begin{array}{l}
f(1)=4 ; \quad a+b=2...(1) \\
f(3)=38 ; \quad 9 a+3 b+2=38-\text { (2) } \\
3 a+b=12
\end{array}
$$
Solving (1) \& (2)
$$
\begin{array}{l}
a=5, b=-3 \\
a-b=8
\end{array}
$$
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