Functions and their inverses

ask maxwong 

maxwong answer me plz

Yay time for the rescue!!

$(x-9)^2=49\\ \sqrt{(x-9)^2}=\pm \sqrt{49}\\ x-9 = \pm 7 \\x = 16 \;or\; x = 2$

Check: (16-9)² = 7² = 49

(2-9)² = (-7)² = 49