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Functions (Edexcel GCSE Maths: Foundation): Flashcards

Exam code: 1MA1

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FrontIntroduction to Functions
Define a function in maths.

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Cards in this collection (6)

Define a function in maths.
A function is a combination of one or more mathematical operations that changes one set of numbers into another set.
It is often pictured as a machine: the rule "multiply by 4 and subtract 3" turns $5$ into $17$ .
Complete the pair of sentences by filling in the missing words:
The number put into a function is called the $______$ .
The number that comes out of it is called the $______$ .
The completed sentences are:
The number put into a function is called the input.
The number that comes out of it is called the output.
A function machine multiplies by $3$ and then subtracts $2$ . What is the output when the input is $5$ ?
The output is $13$ .
Work from left to right: $5 \times 3 = 15$ , and then $15 - 2 = 13$ .
True or False?
A function machine that adds $5$ and then multiplies by $3$ gives the same output as one that multiplies by $3$ and then adds $5$ .
False.
With an input of $4$ , the first machine gives $(4 + 5) \times 3 = 27$ but the second gives $4 \times 3 + 5 = 17$ .
The order of the operations changes the result.
A function machine adds $5$ and then multiplies by $3$ , and the output is $21$ . How do you work out the input?
Work backwards from the output, using the opposite operation at each box and taking the boxes in reverse order.
Here $21 \div 3 = 7$ and then $7 - 5 = 2$ , so the input is $2$ .
A function doubles a number and then adds $1$ . What is the output when the input is $x$ ?
The output is $2 x + 1$ .
The same two operations are applied to the letter exactly as they would be to a number: double $x$ to get $2 x$ , then add $1$ .

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