Algebra · Formulae & rearranging
Chapter 1 · 3
The idea
Substituting into formulae
Why substitution is "replace the letter, keep the structure", why negatives must go in with brackets, and why the order of operations still rules once the numbers are in.
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Algebra · Formulae & rearranging
Substituting into formulae
Why substitution is "replace the letter, keep the structure", why negatives must go in with brackets, and why the order of operations still rules once the numbers are in.
Why it works
Numbers into slots, brackets round them
Substitution may be the most-used skill in the whole course — every formula in maths and science eventually lands here — and its errors are always the same two. A formula is a machine: letters mark the slots where numbers go. To substitute is to replace each letter with its number — brackets round it — and then evaluate with the usual order of operations. Every substitution error is a failure of one of those two clauses.Keep reading — free
The rest of the explanation, plus 2 worked examples you step through move by move.
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