Rút gọn biểu thức sau: \(\frac{\left(a.b+b.c+c.d+d.a\right).a.b.c.d}{\left(c+d\right).\left(a+b\right)+\left(b-c\right).\left(a-d\right)}\)
Cho a.b.c.d \(\in\)R. CMR:
a) \(\left(a^2+1\right)\left(b^2+1\right)\left(c^2+1\right)\ge8abc\)
b) \(\left(a^2+4\right)\left(b^2+4\right)\left(c^2+4\right)\left(d^2+4\right)\ge256abcd\)
Cho 5 số thực khác nhau a,b,c,d,x.Chứng minh :
\(\frac{b+c+d}{\left(b-a\right)\left(c-a\right)\left(d-a\right)\left(x-a\right)}+\frac{a+c+d}{\left(a-b\right)\left(c-b\right)\left(d-b\right)\left(x-b\right)}+\frac{a+b+d}{\left(a-c\right)\left(b-c\right)\left(d-c\right)\left(x-c\right)}+\)
\(\frac{a+b+c}{\left(a-d\right)\left(b-d\right)\left(c-d\right)\left(x-d\right)}=\frac{a+b+c+d-x}{\left(a-x\right)\left(b-x\right)\left(c-x\right)\left(d-x\right)}\)
cho a b c d duong cm rang khong the dong thoi xay ra ca ba bat dang thuc
\(.a+b< c+d\)
\(.\left(a+b\right)\left(c+d\right)< ab+cd\)
\(.\left(a+b\right)cd< \left(c+d\right)ab\)
cho a,b,c,d>0 va abcd=1. chứng minh rằng: \(a^2+b^2+c^2+d^2+a\left(b+c\right)+b\left(c+d\right)+d\left(c+a\right)\ge10\)
Cho a,b,c la cac so nguyen duong thoa man: abc=1. CMR
\(\frac{1}{a^3\left(b+c\right)}+\frac{1}{b^3\left(c+a\right)}+\frac{1}{c^3\left(a+b\right)}\ge\frac{3}{2}\)
\(\left(a+b+c+d\right)^2\left(a+b-c-d\right)^2+\left(a+c-b+d\right)^2+\left(a+d-b-c\right)^2\)\(\left(a+b+c\right)^2+\left(a-b-c\right)^2+\left(b-c-a\right)^2+\left(c-a-b\right)^2\)
Cho a,b,c,d>0 va abcd=1 Chung minh
\(\frac{1}{\left(1+a\right)^2}\)+\(\frac{1}{\left(1+b\right)^2}\)+\(\frac{1}{\left(1+c\right)^2}\)+\(\frac{1}{\left(1+d\right)^2}\)>1
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Cho số a và 3 số b, c, d khác a và thảo mãn điều kiện c + d = 2b. Giải phương trình:
\(\frac{x}{\left(a-b\right)\left(a-c\right)}-\frac{2x}{\left(a-b\right)\left(a-d\right)}+\frac{3x}{\left(a-c\right)\left(a-d\right)}=\frac{4a}{\left(a-c\right)\left(a-d\right)}\)