а)-3x(2x-1)= -6x^2 + 3x
↓ ↓ ↑ ↑ y
________|________|_______|______
- -1 - 1 + 3 + y'
y ↓ (-∞; 1)
y ↑ (1; ∞)
-4x+2y=6
2y=6+4x
y=3+2x
y=2x+3