求各位數(shù)學(xué)大神看一下這道題怎么解

2023-02-23 04:55

2023-02-23 09:15
x(x+1)(x+2)(x+3)
=x(x+3)×(x+1)(x+2)
=x(x+3)[x(x+3)+2]
=[x(x+3)]2+2x(x+3)
=[(√5-3)/2×(√5+3)/2]2+
2(√5-3)/2×(√5+3)/2
=(-1)2+2×(-1)
=-1
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把x 、x+1 、x+2、 x+3你會(huì)看到驚喜,用平方差公式,答案-1

解:∵X=(√5-3)/2
∴X+1=(√5-3)/2+2/2=(√5-1)/2
X+2=(√5-3)/2+4/2=(√5+1)/2
X+3=(√5-3)/2+6/2=(√5+3)/2
∴X(X+1)(X+2)(X+3)
=(√5-3)/2×(√5+3)/2×(√5-1)/2×(√5+1))/2
=(5-9)/4×(5-1)/4
=-4/4×4/4
=-1
x=(√5 -3)/2
x+3 =(√5 +3)/2
x(x+3) = (5-9)/4 = -1
x+1 =(√5 -1)/2
x+2 =(√5 +1)/2
(x+1)(x+2) = (5-1)/4 =1
x(x+1)(x+2)(x+3) = (-1)(1) =-1
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