move 9 over and rearrange so you get -y^2+10y-9 = 0
multiply both sides by -1 and you get y^2-10y+9 = 0
quadratic formula is easiest here
a = 1
b= -10
c = 9
one y will be
y = (10 + sqrt(-10^2 - 4*9))/2
= (10 + sqrt(64))/2
= (10 + 8)/2
= 9
the other y will be
y = (10 - sqrt(-10^2 - 4*9))/2
= (10 - sqrt(64))/2
= (10 -8)/2
= 1
try substituting y for 9 and 1 in the equation y^2-10y+9=0 and you will see that both 9 and 1, when substituted for y, will give you 0
This post was edited by Zpot on Feb 23 2018 12:32am