Chapter 11 - Section 11.3 - Solving Equations by Using Quadratic Methods - Exercise Set - Page 790: 76

$y=1/7, 1$

$y^{-2}-8y^{-1}+7=0$ $y^{-2}*y^2-8y^{-1}*y^2+7*y^2=0*y^2$ $y^{-2+2}-8y^{-1+2}+7y^2=0$ $y^{0}-8y^{1}+7y^2=0$ $1-8y+7y^2=0$ $7y^2-8+1=0$ $y=(-b±\sqrt {b^2-4ac})/2a$ $y=(-(-8)±\sqrt {(-8)^2-4*7*1})/2*7$ $y=(8±\sqrt {64-28})/14$ $y=(8±\sqrt {36})/14$ $y=(8±6)/14$ $y=(8±6)/14$ $y=(8+6)/14$ $y=14/14$ $y=1$ $y=(8±6)/14$ $y=(8-6)/14$ $y=2/14$ $y=1/7$