это алгебра 8 класс)* 1) y=x^2+8x+7 2) y=2x^2-8x 3) ...

Vasy

 1)x2 + 8x + 7 = 0D = b2 - 4acD = 64 - 28 = 36 = 6^2

x1,2 = -b ± √D/2ax1 = -8 + 6/2 = - 2/2 = -1x2 = -8 - 6/2= - 14/2 = -7Ответ: x1 = -1; x2 = -7

2) y=2x^2-8x

  y=2x^2-8x=2x(x-4)=0

                   2x=0    x-4=0

                     x=0     x=4

3)-0.5x2 + 1x + 1.5 = 0Делим на 0.5:-x2 + 2x + 3 = 0D = b2 - 4acD = 4 + 12 = 16 = 4^2

x1,2 = -b ± √D/2ax1 = -2 + 4/-2 = - 2/2 = -1x2 = -2 - 4/-2 = 6/2 = 3Ответ: x1 = -1; x2 = 3 

4)-0.25x2 - 3x - 8 = 0D = b2 - 4acD = 9 - 8 = 1

x1,2 = -b ± √D.2ax1 = 3 + 1/-0.5 = - 4/0.5 = -8x2 = 3 - 1/-0.5 = - 2/0.5 = -4Ответ: x1 = -8; x2 = -4