Question

ВАРИАНТ 27 (даю много баллов)

Answer 1

1. $x^{2} +3x-18=0$

Д.=9-4*1*(-18)=9+72=81=$9^{2}$

х1=$frac{-3+9}{2*1}$=3

х2=$frac{-3-9}{2*1}$=-6

2.$x^{2} -7=0$

$x^{2} =7$

$x= +- sqrt{7}$

3.$x^{2} +x+14=0$

Д.=1-4*1*14=1-56=-55

нет решений

4.

$-34x^{2} =0\x^{2} =0\x=0$

5. $-2x^{2} +7x=0$

х(-2х+7)=0

-2х+7=0  или  х=0

-2х=-7

х=3,5

6.$-77x^{2} +18x-1=0$ / *(-1)

$77x^{2} -18x+1=0$

Д.=324-4*77*1=324-308=16=$4^{2}$

х1=$frac{18-16}{2*77} =frac{1}{77}$

х2=$frac{18+16}{2*77} =frac{17}{77}$

7.$2x^{2} -19x-361=0$

Д.=361-4*2*(361)=361+2888=3248=$57^{2}$

х1=$frac{-19+57}{4} =9,5$

х2=$frac{-19-57}{4} =-19$

8.$-4x^{2} -11x-5=0$ / *(-1)

$4x^{2} +11x+5=0$

Д.=121-4*4*5=121-80=41=$(sqrt{41} )^{2}$

х1=$frac{-11+sqrt{41} }{8}$

х2=$frac{-11-sqrt{41} }{8}$