hmm. not sure if question is written correctly. we dont need the quad formula for this can just solve by
4z^2-7=0
4z^2=7
z^2=7/4
and z=+- sqrt7/2
you can use the quad formula with a=4 b=0 and c=-7
put this into (-b+-sqrt(b^2-4ac))/(2a)
will get the same answer.
if.tou like my answer plz rate as brainliest thx