已知m的平方加m减1=0,求m的3次方+2m的平方减2005
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已知m的平方加m减1=0,求m的3次方+2m的平方减2005
已知m的平方加m减1=0,求m的3次方+2m的平方减2005
已知m的平方加m减1=0,求m的3次方+2m的平方减2005
m²+m-1=0
m²=1-m
m³+2m-2005=m(m²+2m)-2005=m(1-m+2m)-2005=1-2005=-2004
-2004
=m(m方+m)+m方-2005
=m+m²-2005
=1-2005
=-2004
m²+m-1=0
m²+m+1/4-1/4-1=0
(m+1/2)²=5/4
m+1/2=±√5/2
m=±√5/2-1/2
当m=√5/2-1/2,m²=(3-√5)/2,m+2=(3+√5)/2,
m³+2m...
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m²+m-1=0
m²+m+1/4-1/4-1=0
(m+1/2)²=5/4
m+1/2=±√5/2
m=±√5/2-1/2
当m=√5/2-1/2,m²=(3-√5)/2,m+2=(3+√5)/2,
m³+2m²-2005
=m²(m+2)-2005
=(3-√5)/2×(3+√5)/2-2005
=1-2005
= -2004
当m=-√5/2-1/2,m²=(3+√5)/2,m+2=(3-√5)/2,
m³+2m²-2005
=m²(m+2)-2005
=(3+√5)/2×(3-√5)/2-2005
=1-2005
= -2004
即m³+2m²-2005=-2004
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