X^2 - 14x + 49 = 2x^2 + 11x + 23
x^2 + 25x - 26 = 0
D = 25^2 - 4*(-26) = 625 + 104 = 729
x1 = (-25-27)/2 = -26
x2 = (-25+27)/2 = 1
7а(a-b)-3(b²-2ab+a²)=7a²-7ab-3b²+6ab-3a²=4a²+ab-3b²
( Х + 10 )^2 = ( 2 - Х )^2
Х^2 + 20х + 100 = 4 - 4х + х^2
20х + 4х = 4 - 100
24х = - 96
Х = - 96 : 24
Х = - 4
Ответ ( - 4 )
2*4^2-0,5*(-2)+6=2*16+1+6=32+7=39.