a-b=3 b+c=-5 则代数式ac-bc+a^2-ab详解.

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a-b=3 b+c=-5 则代数式ac-bc+a^2-ab详解.
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a-b=3 b+c=-5 则代数式ac-bc+a^2-ab详解.
a-b=3 b+c=-5 则代数式ac-bc+a^2-ab
详解.

a-b=3 b+c=-5 则代数式ac-bc+a^2-ab详解.
a-b=3
b+c=5
相加得
a-b+b+c=3-5
a+c=-2
ac-bc+a²-ab
=c(a-b)+a(a-b)
=(c+a)(a-b)
=(-2)×3
=-6

ac-bc+a^2-ab = c(a-b) + a(a-b) = (a+c)(a-b) = [(a-b)+(b+c)](a-b)
= (3-5) × 3 = -6

等式a-b=3和 b+c=-5相加得到
a-b+b+c=-2,即 a+c=-2
于是
ac-bc+a^2-ab
=(a-b)c+a(a-b)
=(a-b)(a+c)
=3*(-2)
=-6

a=3+b
c=-5-b
然后代入
b会全部消去
等于-6

-6
because a-b=3 b+c=-5
a+c=-2
so (a+c)*(a-b)=ac-bc+a^2-ab=-6

ac-bc+a^2-ab=c(a-b)+a(a-b)=(a-b)(a+c)
=(a-b){(a-b)+(b+c)}=3*(3-5)=-6