The considered equation is equivalent to
(2y+x)2=4x3−27x2+44x−12=(x−2)(4x2−19x+6)=(x−2)((x−2)(4x−11)−16).
The expression above must be a perfect square. Therefore we have either x=2 (and y=−1), or (x−2)=ks2, where k∈{−2,−1,1,2} and s∈N; indeed, if for some prime p and nonnegative integer m the number p2m+1 divides (x−2) but p2m+2 does not, then we have p∣(x−2)(4x−11)−16, so p∣16 and p=2.
We will consider three cases separately.
The case of k=±2. Then we have 4x2−19x+6=±2u2 for some integer u, or, equivalently,
(8x−19)2−265=±32u2,
a contradiction modulo 5.
The case of k=1. Then 4x2−19x+6=u2 for some integer u, which leads to
265=(8x−19)2−16u2=(8x−19−4u)(8x−19+4u).
We easily check that x=6 is the only solution of this equation (we simply consider all possible decompositions: 265=1⋅265=5⋅53=…, etc, and take into account the fact that x−2=s2). Therefore, we obtain two solutions of the original equation: (x,y)∈{(6,3),(6,−9)}.
The case of k=−1. As before, we have 4x2−19x+6=−u2, which is equivalent to
265=(8x−19)2+(4u)2
and we check all possibilities with u≤4: for u=0,1,2 there are no solutions. If u=3, then we obtain (8x−19)2=121=112, which leads to x=1, which gives two solutions: (x,y)∈{(1,1),(1,−2)}. Finally, for u=4 we arrive at (8x−19)2=9=32 and x=2, which gives (x,y)=(2,−1).
Therefore, the set of solutions is as follows:
\{(6, 3), (6, -9), (1, 1), (1, -2), (2, -1)\}.