Find the constant k such that the quadratic 2x^2 + 3x + 8x - x^2 + 4x + k has a double root.
x2+15x+k with a=1,b=15 and c=k we want double root so √b2−4ac=0<=>√152−4k=0<=>√152=√4k=0<=>k=225/4
+1855 
+51 
