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\(\left(a+b+c\right)^2=a^2+b^2+c^2\)
=>\(a^2+b^2+c^2+2\left(ab+bc+ac\right)=a^2+b^2+c^2\)
=>\(2\left(ab+bc+ac\right)=0\)
=>ab+bc+ac=0
\(\dfrac{1}{a^3}+\dfrac{1}{b^3}+\dfrac{1}{c^3}=\dfrac{3}{abc}\)
=>\(\dfrac{\left(bc\right)^3+\left(ac\right)^3+\left(ab\right)^3}{\left(abc\right)^3}=\dfrac{3}{abc}\)
=>\(\left(bc\right)^3+\left(ac\right)^3+\left(ab\right)^3=3\left(abc\right)^2\)
\(\Leftrightarrow\left(ab+bc\right)^3-3\cdot ab\cdot bc\cdot\left(ab+bc\right)+\left(ac\right)^3=3\left(abc\right)^2\)
=>\(\left(-ac\right)^3-3\cdot ab\cdot bc\cdot\left(-ac\right)+\left(ac\right)^3-3\left(abc\right)^2=0\)
=>\(-a^3c^3+a^3c^3+3a^2b^2c^2-3a^2b^2c^2=0\)
=>0=0(đúng)
M=a3+b3+3ab(a2+b2)+6a2b2(a+b)
M=a3+b3+3ab(a2+b2)+6a2b2(a+b)
=(a+b)(a2−ab+b2)+3ab[(a+b)2−2ab]+6a2b2(a+b)
=(a+b)(a2−ab+b2)+3ab[(a+b)2−2ab]+6a2b2(a+b)
=(a+b)[(a+b)2−3ab]+3ab[(a+b)2−2ab]+6a2b2(a+b)
=(a+b)[(a+b)2−3ab]+3ab[(a+b)2−2ab]+6a2b2(a+b)
Thay a + b = 1 vào biểu thức trên ,có :
1.(12−3ab)+3ab(12−2ab)+6a2b2.11.(12−3ab)+3ab(12−2ab)+6a2b2.1
=1−3ab+3ab−6a2b2+6a2b2=1=1−3ab+3ab−6a2b2+6a2b2
=1
Vậy biểu thức M có giá trị bằng 1 khi a + b = 1
M=(a+b)(a2-ab+b2)+3ab(1-2ab)+6a2b2
M=a2-ab+b2+3ab
M=(a+b)2=1
Ta có: a + b = 1
M = a3 + b3 + 3ab(a2 + b2) + 6a2b2(a + b)
= (a + b)3 - 3ab(a + b) + 3ab[(a + b)2 - 2ab] + 6a2 b2 (a + b)
= 1 - 3ab + 3ab(1 - 2ab) + 6a2 b2
= 1 - 3ab + 3ab - 6a2 b2 + 6a2 b2
= 1
nhwos tick nha :D
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Ta có
(m+n+p)^q >= m^q+n^q+p^q
=>a+b+c=1
=>(a+b+c)^2016=1 >= a2016 + b2016 + c2016
Mà a2016 + b2016 + c2016 >=0
=> a2016 + b2016 + c2016=1