Answer
x$^{2}$+x$^{2}$ $\ne$x$^{4}$
Work Step by Step
Since the variables (x$^{2}$) are like terms, they are simply added by their numerical coefficient, so x$^{2}$+x$^{2}$ = 2x$^{2}$. Powers are only added if x$^{2}$ is being multiplied by x$^{2}$ due to the exponent rule that x$^{a}$$\times$x$^{b}$= a$^{a+b}$.
