Question 13
If $\frac1{x+1}+\frac{12}{y+12}+\frac{144}{z+144}=1$, then find the value of $$\frac{x^2}{x^2+x}+\frac{y^2}{y^2+12y}+\frac{z^2}{z^2+144z}.$$
**Editorial clarification.** Assume every displayed fraction is defined. The six quantities $x$, $x+1$, $y$, $y+12$, $z$, $z+144$ must all be nonzero.
Choose one option.
**Editorial clarification.** Assume every displayed fraction is defined. The six quantities $x$, $x+1$, $y$, $y+12$, $z$, $z+144$ must all be nonzero.
Choose one option.