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Function notation (f(x))

Grade 10 · Math · Free lesson

Hey there! Ready to unlock a cool math shorthand? Today, we will explore function notation, which is just a fancy way to write equations.

In math, we often use equations like y = 2x + 3. Function notation replaces the 'y' with 'f(x)', which we read aloud as 'f of x'. Think of a function as an input-output machine where you drop in a number, the machine does some math, and a result pops out.

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To evaluate a function, we must monitor our comprehension. Let us analyze a concrete example: if f(x) = x + 5, and we want to find f(3), we replace every x with 3. If you get confused, pause and re-read the equation to identify the input variable before you calculate.

f(x) = x + 5Input: 3Output: 8

Let us evaluate the key ideas by looking at the parts of f(x) = y. The letter 'f' is just the name of the function, 'x' is the input number we choose, and the final answer 'y' is the output.

f(x) = yf = Namex = Inputy = Output
✏️ Worked example

Evaluate the function f(x) = 3x - 2 for f(4).

  1. Identify the function rule: f(x) = 3x - 2.
  2. Determine the input value from the notation f(4), which tells us that x = 4.
  3. Substitute 4 into the expression in place of x: f(4) = 3(4) - 2.
  4. Multiply 3 by 4 to get 12.
  5. Subtract 2 from 12 to get the final output of 10. Write the final answer as f(4) = 10.
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