## Algebra and Trigonometry 10th Edition

$30\sqrt 6$ feet
In part $a)$ we found the equation connecting $l$ and $x$: $l^2-x^2=225$ Substitute $l=75$ and solve the equation for $x$: $75^2-x^2=225$ $x^2=75^2-225$ $x^2=5625-225$ $x^2=5400$ $x=\pm\sqrt{5400}$ $x=\pm 30\sqrt 6$ As $x\geq 0$, the only solution is: $x=30\sqrt 6$ feet