Question

1) 3x^2+5x-8=0
2) x^2+5x+10=0
3) 7x^2-14x+7=0
4) -x^2+3x+4=0
5) 4(x-1)^2-16x=0

Answer 1

1.
$3x^2+5x-8=0\ D=25+96=121\ x_1=(-5+11):6=1\ x_2=(-5-11):6=- frac{8}{3}$
2.
$x^2+5x+10=0\ D=25-40=-15$
Т.к. D<0 решения нет
3.
$7x^2-14x+7=0\ D=196-196=0\ x=14:14=1$
4.
$-x^2+3x+4=0\ x^2-3x-4=0\ D=9+16=25\ x_1=(3+5):2=4\ x_2=(3-5):2=-1$
5.
$4(x-1)^2-16x=0 \ x^2-2x+1-4x=0\ x^2-6x+1=0\ D=36-4=32\ x_1=(6+4 sqrt{2} ):2=3+2 sqrt{2} \ x_2=(6-4 sqrt{2} ):2=3-2 sqrt{2}$