Use formulae
Objective. Substitute into familiar formulae and interpret the result.
- 1. Learn
- 2. Worked example
- 3. Practice
- 4. Feedback
- 5. Continue
Learn: the key idea
Use formulae is built on a small number of dependable facts. Move fluently between words, symbols and values. Represent the information first, choose a method deliberately, show each step and use an inverse operation or estimate to check that the result fits the question.
Worked example
Evaluate 4x + 1 when x = −7.
- 1Identify the mathematical information and what must be found.
- 2Represent it with a number line, diagram, table or expression where helpful.
- 3Apply the relevant fact carefully and keep each line clear.
- 4Check the result against the conditions in the question: -27.
Answer: -27
Concept mastery
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Practice
Practice happens on its own screen, one question at a time. Answers stay hidden until you submit yours, and you can stop and pick up at the same question later.
Start practisingCommon mistake. A common mistake in use formulae is to apply a remembered procedure before reading the signs, units or order carefully. Write the structure first, then calculate and check.
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