Question

1) 6x+12x²=0; 2) x²-4x-9=0; 3) 40x²+2x+3=0; 4) 6x²-11=7x²-5;

Answer 1

1) 6x+12x^2=0
6x(1+2x) =0
x(1)=0 x(2)=-1/2

2) x^2-4x-9=0
D=16+4*9=16++36=52=4*13
x(1)=4+2√13/2=2+√13
x(2)=2-√13

3) 40x^2+2x+3=0
D=4-4*40*3<0
нет корней

4) 6x^2-11=7x^2-5
7x^2-6x^2=-11+5
x^2=-6
нет корней