91Ó°ÊÓ

The functional value at a point is obtained by putting the value in the expression of the function.

It is clear, from the given information, that the temperature of $0{}^{∘}C$ is equivalent to the temperature of $32{}^{∘}F$ and the temperature of $100{}^{∘}C$ corresponds to the temperature of $212{}^{∘}F$.

As obtained previously, the linear equation that corresponds the temperature in degree Celsius $x$to the temperature in degree Fahrenheit $y$is $y=\frac{9}{5}x+32$.

Let the temperature that is the same on both scales be $p$. Then, $x=y=p$.

Put $x=y=p$in $y=\frac{9}{5}x+32$to get,

$p=\frac{9}{5}p+32$

$p-\frac{9}{5}p=\frac{9}{5}p+32-\frac{9}{5}p$ (Subtract $\frac{9}{5}p$from both sides)

$-\frac{4}{5}p=32$ (Simplify)

$-\frac{4}{5}p\left(-\frac{5}{4}\right)=32\left(-\frac{5}{4}\right)$ (Multiply both sides by$−\frac{5}{4}$)

$p=-40$ (Simplify)

This implies that the temperature that is the same on both scales is -40.