Algebra ToolkitCambridge IGCSE Maths: Flashcards

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What does a letter (variable) represent in algebra?

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What does a letter (variable) represent in algebra?: A generalised or unknown number that can take different values.
What is the difference between an expression and an equation?: An expression is a combination of letters and numbers with no equals sign; an equation states two expressions are equal (has an equals sign).
What is a formula?: A rule connecting two or more different quantities, e.g. $A = lw$ .
What does 'substitution' mean in algebra?: Replacing each letter in an expression or formula with a given numerical value, then evaluating.
What order of operations should you follow when evaluating an expression?: BIDMAS: Brackets, Indices, Division/Multiplication, Addition/Subtraction.
Why should you put a negative substituted value in brackets?: To avoid sign errors, e.g. $(-2)^2 = 4$ but $-2^2$ can be misread as $-4$ .
What are 'like terms'?: Terms with identical letter parts raised to the same power, e.g. $3x$ and $5x$ .
Simplify $2a + 3b + 5a - 9b$: $7a - 6b$
Can $x$ and $x^2$ be combined as like terms? Why or why not?: No, because they have different powers of $x$ , so they are not like terms.
Write an expression for '3 less than $n$ ': $n - 3$
Write an expression for 'double $n$ , then add 5': $2n + 5$
If $a=3$ and $b=-2$ , evaluate $2a^2 - b$: $2(3)^2 - (-2) = 18 + 2 = 20$
What is a coefficient?: The number multiplying a letter in a term, e.g. in $7a$ the coefficient is 7.
Form a formula: total cost $C$ is a £3 fee plus £5 per hour $h$: $C = 3 + 5h$