Evaluate the derivative of₁ = x² + 3y. y+1 Select one: dy (1+y)(-1+2x+2ry) 3+x+6y+3y² dy Ob. O c. dy O d. dy (1-y)(-1+2x+2xy) 3+x+6y+3y² (1+y)(-1+2x+2xy) 3+x+6y+3y² (1+y)(-1-2x-2xy) 3+x+6y+3y2 D