1) 5x^2-2x-7=0
D= (-2)^2 -4*5*(-7)=144>0
x1=2+12/10=1.4
x2= 2-12/10= -1
2) 11x^2+10x-1=0
D=10^2-4*11*(-1)=144>0
x1= -10+12/20=1.1
x2= -10-12/20= -1.1
3)10x^2-9x-1=0
D=100-4*(-9)*(-1)=64>0
x1=9+8/20=0.85
x2=9-8/20=0.05
4) 30x^2 +44x-10=0
D= 44^2 - 4*30*(-10)=3136>0
x1= -44+56/60=0.2
x2= -44-56/60= -1/6