Landslide (-9/100x²)+9=0 
(-9/100x²) +9(*100x²)=0
-9+900x²/100x²=0
-9+900x²/100x²=0
100x²≠0                x≠0
-9+900x²=0
900x²=9
 x²=9/900
 x²=1/100
 x=±√(1/100)=±1/10=±0.1
x1=0.1 x2=-0.1