Given,
x2+4y2+2x+8y−λ=0 is a ellipse
Now on rearranging the terms we get,
⇒λ+5(x+1)2+4λ+5(y+1)2=1
We know that length of latus rectum is a2b2=4
So, 4(λ+5)2(λ+5)=4
⇒42(λ+5)=4(λ+5)
⇒(λ+5)=8(λ+5)
⇒(λ+5)2=64(λ+5)
⇒λ2+25+10λ=64(λ+5)
⇒λ2−54λ−295=0
⇒λ=59or −5
But λ=−5
So, l=2a=2λ+5=264=16
⇒λ+l=59+16=75