when

a = b

 

multiply both sides by 8a

8a^2 = 8ab

 

add (a^2 - 9ab) to both sides

8a^2 + (a^2 - 9ab) = 8ab + (a^2 - 9ab)

 

simplify them to

9(a^2 - ab) = (a^2 - ab)

 

divide both sides by (a^2 - ab)

9 = 1

 

Smiley