Your equation is already in the form ax^2 + bx + c = 0
In your case,
a = 4, b = -7 and c = -2.
The quadratic formula for the solution values of x, which you should memorize or learn to derive, is
x = [-b +/- sqrt (b^2-4ac)]/2a
It would good practice for you to do the final alculation yourself
b^2-4ac = 81 in this case, and has a square root that is an integer, making the answer rather easy to write down.
use the quadratic formula to solve the equation
4x^2-7x-2=0
2 answers
x = -b/2a +/- (1/2a)sqrt(b^2 - 4 a c)
a = 4
b = -7
c = -2
x = 7/8 +/- (1/8) sqrt ( 49 + 32)
x = 7/8 +/- (1/8) sqrt (81)
lucky (9*9)=81
so
x = 7/8 +/- 9/8
x = 16/8 or -2/8 wow, nice polite numbers
so
x = 2 or - 1/4
a = 4
b = -7
c = -2
x = 7/8 +/- (1/8) sqrt ( 49 + 32)
x = 7/8 +/- (1/8) sqrt (81)
lucky (9*9)=81
so
x = 7/8 +/- 9/8
x = 16/8 or -2/8 wow, nice polite numbers
so
x = 2 or - 1/4