HP Forums

New HP Prime user here, I was testing solve functions in cas, but found that

fsolve(x^2+4x+4=0, x) returns -2 as expected, but
fsolve(x^2+4x+4=0, x, -5..5) returns empty brackets.
solve() behaves the same as well.
Why is this happening?

And also, knowing when to use solve, fsolve, Solve app, etc. seems very confusing... could somebody explain when to use what?

bisection does not work if the function does not change sign, which is the case here because you have a root of multiplicity 2. This is detected by exact algorithms, i.e. in solve (without interval, interval forces numeric solving), not by numeric algorithms.