Question

Помогите с уравнениями: 7x^2-16x+4=0 , 2x^2+13x+15=0 , 3x^2+5x+2=0 , 3x^2+8x+4=0 , 2x^2+5x-7=0

Answer 1

7х²-16х+4=0
D=256-4*7*4=256-112=144
D=√144=12
$x = \frac{16 + 12}{14} = 2$
$x = \frac{16 - 12}{14} = \frac{4}{14} = \frac{2}{7}$

2x²+13x+15=0
D=169-4*2*15=169-120=49
D=√49=7
$x = \frac{ - 13 + 7}{4} = - \frac{6}{4} = - \frac{3}{2}$
$x = \frac{ - 13 - 7}{4} = - \frac{20}{4 } = - 5$

3x²+5x+2=0
D=25-4*3*2=25-24=1
$x= \frac{ - 5 - 1}{6} = - \frac{6}{6} = - 1$
$x = \frac{ - 5 + 1}{6} = - \frac{4}{6} = - \frac{2}{3}$

3x²+8x+4=0
D=64-4*3*4=64-48=16=4²
$x = \frac{ - 8 - 4}{6} = - \frac{12}{6} = - 2$
$x = \frac{ - 8 + 4}{6} = - \frac{4}{6} = - \frac{2}{3}$

2x²+5x-7=0
D=25-4*2*(-7)=25+56=81=9²
$x = \frac{ - 5 + 9}{4} = 1$
$x = \frac{ - 5 - 9}{4} = \frac{ - 14}{4} = - \frac{7}{2}$