Expressions & Variables
What is a variable?
A letter that represents an unknown value.
Solve:
x + 7 = 12
5
“Twice a number is 10.”
Write the equation.
2x = 10
Which way do you move for positive x-values on a graph?
To the right
What is the constant of proportionality k?
6
Write an expression for:
“Five more than a number x.”
x + 5
Solve:
3x = 18
6
“A number divided by 5 plus 2 is 9.”
x/5 + 2 = 9 → x = 35
Which quadrant is (–3, 4) in?
Quadrant II
Find k:
x = 2, y = 10
k = 10 ÷ 2 = 5
Simplify:
3x + 4x
7x
Solve:
4x – 6 = 10
4
“Triple a number increased by 7 equals 19.”
3x + 7 = 19 → x = 4
Plotting (5, –2):
x = right or left?
y = up or down?
Right 5, Down 2
Write equation:
k = 4
y = 4x
Which part is the coefficient in 2nd term: 5b+8m-6?
8
Solve:
2(x + 3) = 14
4
“A number divided by 4 is 6.”
x = 24
What do you call (x, y)?
Ordered pair
A graph shows the point (3, 12).
Find k.
12 ÷ 3 = 4 → y = 4x
Write an expression for:
“Triple a number decreased by 4.”
3x – 4
20
“Eight less than double a number equals 10.”
2x – 8 = 10 → x = 9
Which of the following points is farthest from the origin?
A) (3, 4)
B) (–5, 0)
C) (0, –6)
C) (0, –6)
A table shows:
x: 2, 4, 6
y: 5, 10, 16
Is it proportional?
No, because 5/2 = 2.5, 10/4 = 2.5, but 16/6 ≠ 2.5.
The ratio is not constant.