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9x²-5x³=4
5x³-9x²+4=0
5x³-5x²-4x²+4=0
(5x³-5x²)-(4x²-4)=0
5x²(x-1)-4(x²-1)=0
5x²(x-1)-4(x+1)(x-1)=0
(x-1)[5x²-4(x+1)]=0
x1=1
5x²-4(x+1)=0
5x²-4x-4=0
5x²-4x=4
x²-4x/5=4/5
x²-4x/5+(2/5)²=4/5+4/25
(x-2/5)²=24/25
x-2/5=屉24/5
x=2/5±2â6/5
x=(2±2â6)/5
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