A function can be written as f(x), which is shorthand for the function of x is such that followed by an expression for the function eg f(x)=2x+4. The right hand side states what will be done to x: multiply by 2 and add 4.
A function is written with a single letter (normally f) followed by a variable (normally x) in brackets on the left hand side of the equation sign; and an expression (the function to be applied to that variable) on the right hand side.
When a function is evaluated, replace the variable with the number: using the above function,
f(3)=2×3+4=10 or
f(-5)=2×-5+4=-6
Sometimes the function may be written slightly differently with a colon and an arrow:
x:→2x+4 or even as x↦2x+4.
f(x) is defined as f(x)=3x2+2.
What is the value of f(7)?
f(x)=3x2+2
f(7)=3(7)2+2
= 3 x 49 + 2
=149
Answer: 149
Given a function f(x)=x2+4, find the value of f(7).
f(x)=x2+4
f(7)=72+4 (Replace x with 7)
=49+4
=53
Answer: 53