1) 4x^2= 6,25;2)x^2 - x - 90 =0;3) 2x^2 - 5x

1)4x^2=6.25
x^2=6.25/4
x^2=1.5625
x=1.25
2)x^2-x-90=0
d=b^2-4ac=1-4*1*(-90)=1+360=361
x1,2=(-b(+/-)sqrt(d))/2a=(1(+/-)19)/2=10;9
3)2x^2-5x=0
d=b^2-4ac=25-4*2*0=25
x1,2=(-b(+/-)sqrt(d))-2a=(5(+/-)5)/4=0; 10/4=5/2=2.5
4)4x^2-x-3=0
d=b^2-4ac=1-4*4*(-3)=1+48=49
x1,2=(-b(+/-)sqrt(d))/2a=(1(+/-)7)/8=1; 3/4=0.75
5)11x=7x^2
7x^2-11x=0
d=b^2-4ac=121-4*7*0=121
x1,2=(-b(+/-)sqrt(d))/2a=(11(+/-)11)/14=0; 22/14=11/7

1)4x^2=6,25

x^2=1,5625

x1=1,25

x2=-1,25

2) x^2-x-90=0

D=1+360=19^2

x1=(1+19)/2=10

x2=(1-19)/2=-8

3)2x^2-5x=0

x(2x-5)=0

x1=0

2x=5

x2=2,5

4) 4x^2-x-3=0

D=1+48=7^2

x1=(1+7)/4=2

x2=-6/2=-3

5)11x=7x^2

7x^2-11x=0

x(7x-11)=0

x1=0

x2=11/7