Tips

• The sign, number, and units are all affected when placing a value into an expression

• When placing a value into an expression, always use parentheses when the value is a negative number. This is especially important when that value is being subtracted (5 – (–9))…–9 is the value being inserted into the expression.

EXAMPLES

When x = –1, what is x² => (–1)² = 1,

When x = –1, what is -x² => –(–1)² = –(1) = –1

When x = 5 apples, what is x² => (5 apples)² = 25 apples²

Functions: f(x) & f(x, y) Notations

• y = f(x) = x + 3 –> f(x) is used to show there is 1 variable in the expression, x + 3.

• y = f(a, b) = a + 3b –> f(a, b) is used to show that there are 2 variables in the expression

• For every value of y, a function can only have 1 value of x

• y and f(x) or y and f(x, y) are interchangeable