Which numerical expression would provide the solutions to the equation 7x^2 + 4x - 8 = 14

We have that
7x^2 + 4x - 8 = 14-----------------> 7x²+4x-22=0
Step 1
Solving a second degree equation
x1=[-b+√(b²-4ac)]/2a
x2=[-b-√(b²-4ac)]/2a
a=7
b=4
c=-22
then
x1=[-4+√(4²-4*7*(-22))]/(2*7)-----------> [-4+√(632)]/(14)
x1=-(-4+25.14)/14=1.51 

x2=[-4-√(4²-4*7*(-22))]/(2*7)-----------> [-4-√(632)]/(14)
x2=-(-4-25.14)/14=-2.08 

the solutions of the system is 
x1=1.51
x2=-2.08
to check the result

using a graph tool
see the attached figure

the answer is 
the numerical expressions is
x1=[-b+√(b²-4ac)]/2a
x2=[-b-√(b²-4ac)]/2a