х²-2х-5=0
7у²-4х-3=0
(2х+5)(х+2)=21
(4х-3)²+(2х-1)(2х+1)=24

1)4х²-2х-5=0

D=4 +80 = 84

√D=√84

x1= (2+√84)/8

x2=(2-√84)/8

2)7x²-4х-3=0

D= 16+84= 100

√D=10

x1=4+10/14 = 1

x2= 4-10/14=-3/7

3)(2х+5)(х+2)=21

2x²+9x-11=0

D= 81+88 = 169

√D = 13

x1= (-9-13)/4= -5,5

x2=-9+13/4 = 1

4)(4х-3)²+(2х-1)(2х+1)=24

4x²-24x + 9 + 4x²-25= 0

8x²-24x-16= 0

x²-3x-2= 0

D=9+8= 17

√D=√17

x1= (3+√17)/2

x2= (3-√17)/2