( а + b )^2 + ( a - b )^2 < = 3( a^2 + b^2 )
a^2 + 2ab + b^2 + a^2 - 2ab + b^2 <= 3( a^2 + b^2 )
2a^2 + 2b^2 < = 3( a^2 + b^2 )
2( a^2 + b^2 ) < = 3( a^2 + b^2 )
2 < 3
2х+3-2=15-3х,
2х+3х=15-3+2,
5х=14,
х=14/5,
х=2,8
0,6X^2 + 0,8X - 7,8 = 0
6X^2 + 8X - 78 = 0
2 * ( 3X^2 + 4X - 39 ) = 0
D = 16 + 468 = 484 ; √ D = 22
X1 = ( - 4 + 22 ) : 6 = 3
X2 = ( - 4 - 22 ) : 6 = - 4 ( 1/3 )
3x ²+3x-6=3(x ²+x-2)=3(x+2)(x-1)