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x(x+1)(x+2)(x+3)=7920 此方程怎么解?

x(x+1)(x+2)(x+3)=7920 x(x+3)(x+1)(x+2)-7920=0 (x²+3x)(x²+3x+2)-7920=0 (x²+3x)²+2(x²+3x)-7920=0 (x²+3x+90)(x²+3x+88)=0 x²+3x+90=0或(无实解)x²+3x-88=0 (x-8)(x+11)=0 x-8=0或x+11=0 得x...

X×(x-1)×(X-2)×(X-3)=7920 x(x-3)(x-1)(x-2)=7920 (x²-3x)(x²-3x+2)-7920=0 (x²-3x)²+2(x²-3x)-7920=0 (x²-3x+90)(x²-3x-88)=0 (x²-3x+90)(x-11)(x+8)=0 因为x²-3x+90=(x-3/2)²+90-9/4>0 ...

总面积=4*3+2*3+X*X+2X;X=6时,总面积=66,总费用=66*120=7920,总费用为7920元。

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