You shouldn't need a calculator for this. The quadratic equation is written in standard form.
ax^2 + bx + c = 0
You substitute a, b, and c into the discriminant formula and solve as shown in the example in the picture you provided.
(-7)^2 - 4(2)(-8)
49 - 4(-16)
49 - (-64)
49 + 64
113
Best of Luck!
