The reversible chemical reaction A+B⇌C+D has the following equilibrium constant: Kc=[C][D][A][B]=5.0?

A + B ⇌ C + D …. Kc

Initial concentrations :
[A]ₒ = 1.00 M
[B]ₒ = 2.00 M
[C]ₒ = [D]ₒ = 0 M

Equilibrium concentrations (assuming that y M of A and y M of B are consumed) :
[A] = (1.00 - y) M
[B] = (2.00 - y) M
[C] = [D] = y M

Kc = [C][D] / {[A][B]}
5.0 = y² / {(1.00 - y)(2.00 - y)}
5 = y² / (2 - 3y + y²)}
5y² - 15y + 10 = y²
4y² - 15y + 10 = 0
y = [15 ± √(15² - 4×4×10)] / (2×4)
y = 2.88 (rejected) or y = 0.87

[D] at equilibrium = 0.87 M