Question

Question #a8045

Answer 1

`-40°`

Explanation:

We know `F=9/5C+32`
We need to find a point in which `F=C`
So, we let `F=C` and rewrite the equation to look like this:
`C=9/5C+32`

From here, we just solve for C. Now, in a many cases, when we substitute `F` with `C`, there is no solution and we get something that looks like `1=2`. This means that there is no point in which `F=C`

Let's solve this.
`C=9/5C+32`
`C-9/5C=32`

Factorize `C` out.

`C(1-9/5)=32`
`-4/5C=32`
`C=32*-5/4=-40`

`:.` When `C=-40` `F` is also `-40`

We can check:
`F=9/5C+32`
`-40=9/5*-40+32`
`-40=-40`

`QED`

Answer 2

`C=-40`

Explanation:

`F=9/5C+32`

Let `F=C` so `C=9/5C+32`

Bring all `C` terms to one side

`-4/5C=32`

Divide both sides by `-4/5` to get `C` on its own

`C=-40`