If the equation 2x2+4xy+7y2−12x−2y+t=0, where t is a parameter has exactly one real solution of the form (x, y), then the sum of (x + y) is equal to _______.

2x2+4x(y−3)+7y2−2y+t=0D = 0 (for one solution)⇒ 16(y−3)2−87y2−2y+t=0or   2(y−3)2−7y2−2y+t=0or   2y2−6y+9−7y2−2y+t=0or   −5y2−10y+18−t=0or   5y2+10y+t−18=0Again D = 0 (for one solution)⇒ 100−20(t−18)=0or 5 - t + 18 = 0or t = 23for t=23;5y2+10y+5=0(y+1)2=0  or  y=−1for y=−1;2x2−16x+32=0x2−8x+16=0x=4  or  x+y=3