a b c⒈已知abc=1,求_______+_________+_________的值.ab+a+1 bc+b+1 ac+c+1⒉求值:a-b a的平方+b的平方_______- ______________________2a+2b a的平方-b的平方2x-3 A B⒊已知__________=_______+_______求A、B的值.(x-1)(x+2) x-1 x+2那
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![a b c⒈已知abc=1,求_______+_________+_________的值.ab+a+1 bc+b+1 ac+c+1⒉求值:a-b a的平方+b的平方_______- ______________________2a+2b a的平方-b的平方2x-3 A B⒊已知__________=_______+_______求A、B的值.(x-1)(x+2) x-1 x+2那](/uploads/image/z/7297056-0-6.jpg?t=a+b+c%E2%92%88%E5%B7%B2%E7%9F%A5abc%3D1%2C%E6%B1%82_______%2B_________%2B_________%E7%9A%84%E5%80%BC.ab%2Ba%2B1+bc%2Bb%2B1+ac%2Bc%2B1%E2%92%89%E6%B1%82%E5%80%BC%3Aa-b+a%E7%9A%84%E5%B9%B3%E6%96%B9%2Bb%E7%9A%84%E5%B9%B3%E6%96%B9_______-+______________________2a%2B2b+a%E7%9A%84%E5%B9%B3%E6%96%B9-b%E7%9A%84%E5%B9%B3%E6%96%B92x-3+A+B%E2%92%8A%E5%B7%B2%E7%9F%A5__________%3D_______%2B_______%E6%B1%82A%E3%80%81B%E7%9A%84%E5%80%BC.%28x-1%29%28x%2B2%29+x-1+x%2B2%E9%82%A3)
a b c⒈已知abc=1,求_______+_________+_________的值.ab+a+1 bc+b+1 ac+c+1⒉求值:a-b a的平方+b的平方_______- ______________________2a+2b a的平方-b的平方2x-3 A B⒊已知__________=_______+_______求A、B的值.(x-1)(x+2) x-1 x+2那
a b c
⒈已知abc=1,求_______+_________+_________的值.
ab+a+1 bc+b+1 ac+c+1
⒉求值:
a-b a的平方+b的平方
_______- ______________________
2a+2b a的平方-b的平方
2x-3 A B
⒊已知__________=_______+_______求A、B的值.
(x-1)(x+2) x-1 x+2
那些符号和数字顺着横线1个个对回去就OK了,
比如:
a b c
_______+___________________+____________
ab+a+1 bc+b+1 ac+c+1
a b c⒈已知abc=1,求_______+_________+_________的值.ab+a+1 bc+b+1 ac+c+1⒉求值:a-b a的平方+b的平方_______- ______________________2a+2b a的平方-b的平方2x-3 A B⒊已知__________=_______+_______求A、B的值.(x-1)(x+2) x-1 x+2那
1.因为:abc=1
a/ab+a+1= a/ab+a+abc= 1/bc+b+1
c/ca+c+1= c/(1/b)+c+1= bc/bc+b+1
所以:
原式
= a/(ab+a+1)+ b/(bc+b+1)+ c/(ca+c+1)
= 1/(bc+b+1)+ b/(bc+b+1)+ bc/(bc+b+1)
= bc+b+1/bc+b+1
= 1
2.(a-b)/(2a+2b)-(a^2+b^2)/(a^2-b^2)
=(a-b)²/[2(a-b)(a+b)]-2(a²+b²)/[2(a-b)(a+b)]
=-(a+b)²/[2(a-b)(a+b)]
=-(a+b)/[2(a-b)]
3.已知(2x-3)/(x-1)(x+2)=A/(x-1)+B/(x+2),求A、B的值.
A/(x-1)+B/(x+2)
=A(x+2)/(x+2)(x-1)+B(x-1)/(x+2)(x-1)
=[A(x+2)+B(x-1)]/(x+2)(x-1)
=[(A+B)x+(2A-B)]/(x+2)(x-1)=2x-3/[(x-1)(x+2)]
A+B=2,2A-B=-3
3A=-1
A=-1/3
B=2+1/3=7/3
确实有些乱,重写一下吧!!
这是什么意思?
1。不妨令a=b=c=1,代入a/(ab+a+1)+b/(bc+b+1)+c/(ac+c+1)=1/3+1/3+1/3=1
2。(a-b)/(2a+2b)-(a^2+b^2)/(a^2-b^2)
=(a-b)²/[2(a-b)(a+b)]-2(a²+b²)/[2(a-b)(a+b)]
=-(a+b)²/[2(a-b)(a+b)]
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1。不妨令a=b=c=1,代入a/(ab+a+1)+b/(bc+b+1)+c/(ac+c+1)=1/3+1/3+1/3=1
2。(a-b)/(2a+2b)-(a^2+b^2)/(a^2-b^2)
=(a-b)²/[2(a-b)(a+b)]-2(a²+b²)/[2(a-b)(a+b)]
=-(a+b)²/[2(a-b)(a+b)]
=-(a+b)/[2(a-b)]
3。右边通分后分子=A(x+2)+B(x-1)=(A+B)x+(2A-B)
左边分子=2x-3
由于分母一样,分式相等,所以有:A+B=2,2A-B=-3
解得A=-1/3,B=7/3
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