1)(5-2x)(7x-1)=(2x-5)²
35x-5-14x²+2x-4x²+20x-25=0
-18x²+57x-30=0
6x²-19x+10=0
D=361-240=121
x1=(19-11)/12=2/3
x2=(19+11)/12=5/2
3)2y³-5y²-2y+5=0
y²(2y-5)-(2y-5)=0
(2y-5)(y²-1)=0
2y-5=0
2y=5
y=2,5
y²-1=0
y²=1
y=-1
y=1
4)x⁴-25x²+60x-36=0
x^4-(5x-6)²=0
(x²-5x+6)(x²+5x-6)=0
x²-5x+6=0
x1+x2=5 U x1*x2=6
x1=2 U x2=3
x²+5x-6=0
x1=x2=-5 U x1*x2=-6
x1=-6 U x2=1