# Math Help - Quadratic Equation

Express the quadratic equation $y = x^2$as a linear equation using the substitution $s = ln y$, $t = ln x$.

I have no idea how to start this.
Any help is appreciated!

2. Originally Posted by live_laugh_luv27
Express the quadratic equation $y = x^2$as a linear equation using the substitution $s = ln y$, $t = ln x$.

I have no idea how to start this.
Any help is appreciated!
Taking the natural log of both sides gives

$\ln y = \ln x^2 = 2 \ln x$

3. Originally Posted by danny arrigo
Taking the natural log of both sides gives

$\ln y = \ln x^2 = 2 \ln x$

Ok...but where do the s and t come in??

4. Originally Posted by live_laugh_luv27
Ok...but where do the s and t come in??
If you let

$s = \ln y\; \text{and}\; r = \ln x$ gives $s = 2r$, a linear equation.

5. Ok, thanks