F(x)=5x+1 find f(-4)
any idea how to solve this question?

Yes, I have an idea.

Take the (-4) and put it into the F(x) in place of the 'x'.

Try it and let us know if it works.

I have an idea also.

so f(x) means the function of x
a function is when you put a value into the function (think of it like a machine) it processes the value and spits a value out so
f(-4) means put -4 into the funciton so put -4 for x in the funciton so
f(-4)=5(-4)+4
f(-4)=-20+1
f(-4)=-19

It's like discovering the answer to a puzzle. the purpose in solving an equation is to find the value or values of the variable that makes it a true statement. any value of the variable that makes the equation true is called a solution to the equation.