4x^2-11=x^2-11+9x

x^2-2x+1=0

7x+3=2x^2+3x+3

x^2-4x+4=0

1) 4x^2-11=x^2-11+9x

3x^2=9x

x^2=3x

x^2/x=3

x=3

2) x^2-2x+1=0

D = (-2) ^2-4*1*1=0

x = - (-2) / (2*1)

x=1

3) 7x+3=2x^2+3x+3

-2x^2+7x-3x+3-3=0

-2x^2=-4x

x^2=2x

x^2/x=2

x=2

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

D = (-4) ^2-4*1*4=16-16=0

x = - (-4) / (2*1)

x=2

если D=0 то корень один