If k x2+2=4x+k x−7x2  has real and equal roots, then k=

Given equation is k x2+2=4x+k x−7x2 ⇒(7+k)x2−(4+k)x+2=0 ….. ( 1 )The roots of given equation are Real and Equal, so the discriminant Δ=0 i.e b2−4ac=0 (4+k)2−8(7+k)=0     ( ∵  from Eq.1 )⇒k2−40=0 ∴ k=±2 10