Respuesta :

y=-4x²-3x+3
y-3=-4x²-3x
y-3=-4(x²+3/4)x)
y-3-4*(3/8)²=-4(x²+2(3/8)x+(3/8)²)
y- 3.5625 =-4(x+(0.375))²
y= -4(x+(0.375))² + 3.5625

vertex (-0.375, 3.5625)