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Algebra I: Functions & graphs

Grade 10 · Math · Free lesson

Hey there! Today we are going to explore one of the coolest ideas in math: functions. Think of a function as a magical math machine that takes an input, does a specific job, and spits out a unique output!

At its heart, a function is a rule that connects inputs to outputs. For every single input you put into the machine, you get exactly one output back.

mathematics

Imagine our function machine adds 3 to any number we feed it. If we input the number 2, the machine processes it and outputs 5. If we input 4, we get 7!

+ 3 Machine Input Output 2 5

We can graph these input-output pairs as coordinate points (x, y) on a grid. The horizontal line is the x-axis (inputs), and the vertical line is the y-axis (outputs).

Inputs (x) Outputs (y) (2, 5) (4, 7)
✏️ Worked example

If our function rule is y = 2x + 1, find the output (y) when the input (x) is 3.

  1. Identify the given function rule: y = 2x + 1.
  2. Replace the input variable 'x' with the number 3 in the equation: y = 2(3) + 1.
  3. Multiply 2 by 3 to get 6.
  4. Add 1 to the result: 6 + 1 = 7.
  5. State the final coordinate pair: When the input is 3, the output is 7, written as (3, 7).
mathematics
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