1) 5x2-10x+9-2x2+14x-20=3x2+4x-11
2) -m5+2m4-6m5+12m3-18m3=-7m5+2m4-6m3
3) 0,2a3+1,4a2-2,2-0,9a3+18a2+3=-0,5a3+19,4a2+0,8
4) 6x2y-xy2-8x2y+2xy2-xy+7=-2x2y+xy2-xy+7
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Х^2 + 8х + 4 = 0
D = 64 - 14 = 50 = 5 V 2
X1 = ( - 8 + 5 V 2 ) : 2 = - 4 + 2,5 V 2
X2 = - 4 - 2,5 V 2
Знак V это корень квадратный
(5x-4)(5x+4)=0
5x-4=0 или 5х+4=0
5х=4 5х=-4
х=0.8 х=-0.8