Question

Решите уравнение х²-15=2х через дискриминант

Answer 1

X^2 - 2x - 15 = 0 
D = 4 + 4*15 = 64 = 8^2
x1 = ( 2 + 8)/2 = 10/2 = 5;
x2 = (2 - 8)/2 = - 6/2 = - 3;

Answer 2

$x^{2} -15=2x \\ x^{2} -15-2x=0 \\ x^{2} -2x-15=0 \\ D=b^2-4ac=64 \\ \sqrt{D} = \sqrt{64}=8 \\ x_1= \frac{-b+ \sqrt{D} }{2a} = \frac{2+8}{2} = \frac{10}{2}=5 \\ x_2= \frac{-b- \sqrt{D} }{2a} = \frac{2-8}{2}= \frac{-6}{2} =-3$