设a-b=3,c-b=1,求代数式3(a-c)²+2(c-a)-5的值
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设a-b=3,c-b=1,求代数式3(a-c)²+2(c-a)-5的值
设a-b=3,c-b=1,求代数式3(a-c)²+2(c-a)-5的值
设a-b=3,c-b=1,求代数式3(a-c)²+2(c-a)-5的值
a-b=3,c-b=1
两式相减得:a-c=2
3(a-c)²+2(c-a)-5=3(a-c)²-2(a-c)-5
=12-4-5
=3
a-b=3 一式,c-b+1 二式,用一式减二式·········你懂得
a-b=3,c-b=1
b=a-3=c-1
=>a-c=2
=>.3(a-c)²+2(c-a)-5=3x4+2x2-5=11
a-b=3,则b=a-3
代入c-b=1
得到c=a-2
代入3(a-c)²+2(c-a)-5
原式=3*(2^2+2*(-2)-5
=3
(a-b)-(c-b)=a-b-c+b=a-c=3-1=2 (c-b)-(a-b)=c-b-a+b=c-a=1-3=-2 带入后得出 3(2)²+2(-2)-5=3
a-b=3, (`1)
c-b=1 (2)
(1)-(2):得a-c=2
3(a-c)²+2(c-a)-5
=3(a-c)²-2(a-c)-5
=[3(a-c)-5][(a-c)+1]
=(3*2-5)(2+1)
=3
a-c=(a-b)-(c-b)=3-1=2
3(a-c)²+2(c-a)-5
=3×2²+2×(-2)-5
=3
b=c-1代入a-b=3得a-c=2,则代数式等于3
c-b=1.b-c=-1.a b b-c=2.a-c=2.所以原式=3*2*2-2*2-5=3