21x-6x²+3=5(4x+1-2x²). (6x-5)(2x-1) -=0

Răspuns :

21x-6x la 2+3=20x+5-10 x la 2
21x-6xla 2+3-20 x -5+10 x la 2=
x  +4 x la 2 -2=0

(6x-5)(2x-1)=
12 xla 2-6x-10x+5
12 x la 2-16x+5=0