How many real roots are there in x^2+bx-1=0

In order to see how many real roots it has you have to see what the Δ is

So if Δ>0 then there are 2 real roots

If Δ=0 there is 1 real root

If Δ<0 no real root

And we know that:

Δ=b^2-4ac

So in the equation: Δ=b^2+4 and b^2 is always a number greater than or equal to 0 so when you add 4 to it, it is always greater than 0

So it has 2 real roots