\(\left[a;a+2\right]va\left[b;b+1\right]\) tìm điều kiện a và b để A giao B khác rỗng
CC
Những câu hỏi liên quan
CMR : frac{b+c+d}{left(b-aright)left(c-aright)left(d-aright)left(x-aright)}+frac{c+d+a}{left(c-dright)left(d-bright)left(a-bright)left(x-bright)}+frac{d+a+b}{left(d-cright)left(a-cright)left(b-cright)left(x-cright)}+frac{a+b+c}{left(a-dright)left(b-dright)left(c-dright)left(x-dright)}frac{x-a-b-c-d}{left(x-aright)left(x-bright)left(x-cright)left(x-dright)}.
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CMR : \(\frac{b+c+d}{\left(b-a\right)\left(c-a\right)\left(d-a\right)\left(x-a\right)}+\frac{c+d+a}{\left(c-d\right)\left(d-b\right)\left(a-b\right)\left(x-b\right)}+\frac{d+a+b}{\left(d-c\right)\left(a-c\right)\left(b-c\right)\left(x-c\right)}\)\(+\frac{a+b+c}{\left(a-d\right)\left(b-d\right)\left(c-d\right)\left(x-d\right)}\)\(=\frac{x-a-b-c-d}{\left(x-a\right)\left(x-b\right)\left(x-c\right)\left(x-d\right)}.\)
\(\frac{b+c+d}{\left(b-a\right)\left(c-a\right)\left(d-a\right)\left(x-a\right)}=\frac{\left(a+b+c+d-x\right)+\left(x-a\right)}{\left(b-a\right)\left(c-a\right)\left(d-a\right)\left(x-a\right)}\)\(=\frac{\left(a+b+c+d-x\right)}{\left(b-a\right)\left(c-a\right)\left(d-a\right)\left(x-a\right)}+\frac{1}{\left(b-a\right)\left(c-a\right)\left(d-a\right)}\)
Áp dụng hoán vị vòng \(b\rightarrow c\rightarrow d\rightarrow a\rightarrow b\) vào VT , ta được :
\(\left(a+b+c+d-x\right)\)[\(\frac{1}{\left(a-b\right)\left(a-c\right)\left(a-d\right)\left(a-x\right)}+\frac{1}{\left(b-a\right)\left(b-c\right)\left(b-d\right)\left(b-x\right)}+\frac{1}{\left(c-a\right)\left(c-b\right)\left(c-d\right)\left(c-x\right)}\)\(+\frac{1}{\left(d-a\right)\left(d-b\right)\left(d-c\right)\left(d-x\right)}\).
Quy đồng mẫu thức và tính toán biểu thức trong [ ] ta được :
\(\frac{-1}{\left(x-a\right)\left(x-b\right)\left(x-c\right)\left(x-d\right)}\)
Vậy ...............
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Tính A= \(\frac{\left(x-a\right)\left(x-b\right)}{\left(c-a\right)\left(c-b\right)}+\frac{\left(x-a\right)\left(x-c\right)}{\left(b-a\right)\left(b-c\right)}+\frac{\left(x-b\right)\left(x-c\right)}{\left(a-b\right)\left(a-c\right)}\)
Cho a,b,c là các số nguyên dương. CM:
a) \(\left(a,b,c\right)=\dfrac{\left(a,b,c\right)abc}{\left(a,b\right)\left(b,c\right)\left(c,a\right)}\)
b) \(\left[a,b,c\right]=\dfrac{\left(a,b,c\right)\left[a,b\right]\left[b,c\right]\left[c,a\right]}{abc}\)
LL
30 tháng 1 2018 lúc 21:13
Thực hiện phép tính:
1) Adfrac{1}{left(a-bright)left(a-cright)}+dfrac{1}{left(b-aright)left(b-cright)}+dfrac{1}{left(c-aright)left(c-bright)}
2) Bdfrac{1}{aleft(a-bright)left(a-cright)}+dfrac{1}{bleft(b-aright)left(b-cright)}+dfrac{1}{cleft(c-aright)left(c-bright)}
3, Cdfrac{bc}{left(a-bright)left(a-cright)}+dfrac{ac}{left(b-aright)left(b-cright)}+dfrac{ab}{left(c-aright)left(c-bright)}
4) Ddfrac{a^2}{left(a-bright)left(a-cright)}+dfrac{b^2}{left(b-aright)left(b-cright)}+dfrac{c^2}{left(c-ar...
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Thực hiện phép tính:
1) \(A=\dfrac{1}{\left(a-b\right)\left(a-c\right)}+\dfrac{1}{\left(b-a\right)\left(b-c\right)}+\dfrac{1}{\left(c-a\right)\left(c-b\right)}\)
2) \(B=\dfrac{1}{a\left(a-b\right)\left(a-c\right)}+\dfrac{1}{b\left(b-a\right)\left(b-c\right)}+\dfrac{1}{c\left(c-a\right)\left(c-b\right)}\)
3, \(C=\dfrac{bc}{\left(a-b\right)\left(a-c\right)}+\dfrac{ac}{\left(b-a\right)\left(b-c\right)}+\dfrac{ab}{\left(c-a\right)\left(c-b\right)}\)
4) \(D=\dfrac{a^2}{\left(a-b\right)\left(a-c\right)}+\dfrac{b^2}{\left(b-a\right)\left(b-c\right)}+\dfrac{c^2}{\left(c-a\right)\left(c-b\right)}\)
1)\(\dfrac{c-b}{\left(a-b\right)\left(c-b\right)\left(a-c\right)}+\dfrac{a-c}{\left(b-a\right)\left(b-c\right)\left(a-c\right)}+\dfrac{b-a}{\left(b-a\right)\left(c-b\right)\left(c-a\right)}=\dfrac{c-b+a-c+b-c}{\left(a-b\right)\left(b-c\right)\left(c-a\right)}=0\)
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Cho a,b,c là các số thực thuộc đoạn [-1,1] .Chứng minh rằng :
\(\left|\left(a-b\right)\left(b-c\right)\right|+\left|\left(b-c\right)\left(c-a\right)\right|+\left|\left(c-a\right)\left(a-b\right)\right|\ge\dfrac{5}{2}\left|\left(a-b\right)\left(b-c\right)\left(c-a\right)\right|\)
C/m nếu a,b là các số nguyên dương thì left(left[a,bright]cright)left[left(a,cright),left(b,cright)right] left[left(a,bright),cright]left(left[a,cright],left[b,cright]right) left[a,b,cright]frac{abc.left(a,b,cright)}{left(a,bright),left(b,cright),left(c,aright)} left(a,b,cright)frac{abc.left[a,b,cright]}{left[a,bright],left[b,cright],left[c,aright]}
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C/m nếu a,b là các số nguyên dương thì
\(\left(\left[a,b\right]c\right)=\left[\left(a,c\right),\left(b,c\right)\right]\)
\(\left[\left(a,b\right),c\right]=\left(\left[a,c\right],\left[b,c\right]\right)\)
\(\left[a,b,c\right]=\frac{abc.\left(a,b,c\right)}{\left(a,b\right),\left(b,c\right),\left(c,a\right)}\)
\(\left(a,b,c\right)=\frac{abc.\left[a,b,c\right]}{\left[a,b\right],\left[b,c\right],\left[c,a\right]}\)
PT
26 tháng 8 2016 lúc 9:27
Cho 5 số thực khác nhau a,b,c,d,x.Chứng minh :frac{b+c+d}{left(b-aright)left(c-aright)left(d-aright)left(x-aright)}+frac{a+c+d}{left(a-bright)left(c-bright)left(d-bright)left(x-bright)}+frac{a+b+d}{left(a-cright)left(b-cright)left(d-cright)left(x-cright)}+frac{a+b+c}{left(a-dright)left(b-dright)left(c-dright)left(x-dright)}frac{a+b+c+d-x}{left(a-xright)left(b-xright)left(c-xright)left(d-xright)}
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Cho 5 số thực khác nhau a,b,c,d,x.Chứng minh :
\(\frac{b+c+d}{\left(b-a\right)\left(c-a\right)\left(d-a\right)\left(x-a\right)}+\frac{a+c+d}{\left(a-b\right)\left(c-b\right)\left(d-b\right)\left(x-b\right)}+\frac{a+b+d}{\left(a-c\right)\left(b-c\right)\left(d-c\right)\left(x-c\right)}+\)
\(\frac{a+b+c}{\left(a-d\right)\left(b-d\right)\left(c-d\right)\left(x-d\right)}=\frac{a+b+c+d-x}{\left(a-x\right)\left(b-x\right)\left(c-x\right)\left(d-x\right)}\)
Rút gọn biểu thức :
\(\frac{a^2\left(a+b\right)\left(a+c\right)}{\left(a-b\right)\left(a-c\right)}+\frac{b^2\left(b+a\right)\left(b+c\right)}{\left(b-a\right)\left(b-c\right)}+\frac{c^2\left(c+a\right)\left(c+b\right)}{\left(c-a\right)\left(c-b\right)}\)
Tính :
\(\frac{\left(x-a\right)\left(x-b\right)}{\left(c-a\right)\left(c-b\right)}+\frac{\left(x-a\right)\left(x-c\right)}{\left(b-a\right)\left(b-c\right)}+\frac{\left(x-b\right)\left(x-c\right)}{\left(a-b\right)\left(a-c\right)}\)
Tính :
\(\frac{\left(x-a\right)\left(x-b\right)}{\left(c-a\right)\left(c-b\right)}+\frac{\left(x-a\right)\left(x-c\right)}{\left(b-a\right)\left(b-c\right)}+\frac{\left(x-b\right)\left(x-c\right)}{\left(a-b\right)\left(a-c\right)}\)