Question

7х²-х-8=0 а=7b=-1c=-8

Answer 1

$7x^2-x-8=0;\\ a=7;\ b=-;\1c=-8\\ D=b^2-4\cdot a\cdot c=(-1)^2-4\cdot7\cdot(-8)=1+224=225=(\pm15)^2;\\ x_1=\frac{-b-\sqrt{D}}{2\cdot a}=\frac{1-15}{14}=\frac{-14}{14}=-1;\\ x_1=\frac{-b+\sqrt{D}}{2\cdot a}=\frac{1+15}{14}=\frac{16}{14}=\frac87=1\frac17;\\ x=-1;\ 1\frac17.$

Answer 2

7x^2 - 1x - 8 = 0;
       D = b^2 - 4ac;
D = -1^2 - 4 * 7 * (-8);
D = 1 + 224 = 225;
D > 0, два корня!
       x1,2 = (-b ± √D)/2a;
x1:x = (1 + 15)/2*7;
     x = 16/14;
     x = 1*(2/14);
x2:x = (1 - 15)/2*7;
     x = -(14/14);
     x = -1;
       Ответ: 1*(2/14); -1.