The value of b^2-4ac is known as the discriminant of a quadratic function, and can tell you how many roots exist of this function depending on what it is equal to.
Start by moving the -1 to the other side, as we need this function to equal zero.
2x^2 + 3x + 1 = 0
This is now the standard form ax^2 + bx + c = 0. Plug each value that corresponds into the discriminant equation.
b^2-4ac
(3)^2 - 4(2)(1)
9 - 8
1
The value of the discriminant is 1, meaning that two real roots exist for the function described.