\(VP=\left(a+b\right)\left[\left(a-b\right)\left(a-b\right)+ab\right]\\ VP=\left(a+b\right)\left[\left(a-b\right)^2+ab\right]\\ VP=\left(a+b\right)\left[a^2+b^2-2ab+ab\right]\\ VP=\left(a+b\right)\left(a^2-ab+b^2\right)=a^3+b^3=VT\)
VP = (a + b) [(a - b) (a - b) + ab]
= (a + b) [(a -b)2 + ab]
= (a + b) [a2 + b2 -2ab + ab]
= (a + b) (a2 - ab + b2)
= a3 + b3
= VT
Có : a3 + b3 = ( a + b ) ( a2 - ab + b2 ) = ( a + b ) ( a2 - ab - ab + b2 + ab ) = ( a + b ) [ a ( a - b ) - b ( a - b ) + ab ] = ( a + b ) [ ( a - b ) ( a - b ) + ab ]
CMR: a3 + b3 = (a + b) [(a - b) (a - b) + ab]
VP = (a+b) [ (a-b)2 + ab ]
VP = (a+b) [(a + b2) + ab]
VP = (a+b) (a2 - b2 - 2ab + ab]
VP = (a+b) (a2 - ab + b2) = a3 + b3
= VT
\(#AnDanh\)
