Chapter 11 - Rational Expressions and Functions - 11-5 Solving Rational Equations - Practice and Problem-Solving Exercises - Page 684: 35

$s=2,-5$

Given:$\dfrac{3}{s-1}-\dfrac{12}{s^2-1}=-1$ Need to find least common denominator(LCD). $\dfrac{3(s+1)-12}{s^2-1}=-1$ $\dfrac{3s+3-12}{s^2-1}=-1$ $\dfrac{3s-9}{s^2-1}=-1$ Apply cross products. $3s-9=-1(s^2-1)$ $3s-9=-s^2+1$ $-s^2+1-3s+9=0$ or, $(s-2)(s+5)=0$ Hence, $s=2,-5$