Check whether the following is quadratic equation or not.
x2 + 6x − 4 = 0
Here it has been given that,
x2 + 6x - 4 = 0
Now, the above equation clearly represents a quadratic equation of the form ax2 + bx + c = 0, where a = 1, b = 6 and c = -4.
Hence, the above equation is a quadratic equation.