You just substitute the value of x in the given equation:
f(x) = 2x^2 - 5
f(-4) = 2 (-4)^2 -5 = 27
f(x) : a name given to the equation
f(-4): refer to the equation when the value of the independent variable x has the value between the brackets.
I am sure you are trying to type

If that is it, then you should recall the law of exponents which says,

Let us share the exponent for each of them.

We now apply the law,

We now simplify to obtain,

If that is not the expression let me know so I will know how to help you
Answer:
x = 50
Step-by-step explanation:
x/5 = 10
Multiply both sides of the equation by 5.
5(x/5) = 5(10)
x = 5(10)
x = 50
The value of x is 50.