Algebraic Expressions and Formulas

Mathematics — First Preparatory

Substitution in expressions and formulas

Substitution means replacing a variable with a known number and then calculating the value of the expression.
A formula is a general rule that links quantities, for example:

Comparison aspect	Main idea	Keywords
Area of a rectangle	A = l × w (length × width)	lengthwidth
Perimeter of a rectangle	P = 2(l + w)
Area of a triangle	A = ½ × base × height	baseheight
•	When substituting take care with powers and signs. If x = −2 then x² = 4 not −4	substitutingtakecarepowers

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