August 18, 2012
8.3 Using Intercepts
Learning outcome
To use x and y intercepts to graph linear equations.
x-intercepts
-The coordinate of a point where a graph crosses the x-axis.
-To find the x intercepts, substitute 0 fro the y, then solve for x
y-intercepts
-The coordinate of a point where a graph crosses the y-axis.
-To find the y intercepts, substitute 0 fro the x, then solve for y
August 18, 2012
Find the intercepts of the graph 2x - 5y = -10. Then graph using
the intercepts
y-intercepts
2(
) - 5y = -10
x- intercept
2x - 5(
) = -10
Find the intercepts of the graph 2x + 3y = 6. Then graph using
the intercepts
y-intercepts
2(
) + 3y = 6
x- intercept
2x + 3(
)=6
August 18, 2012
You run and walk on a fitness trail that is 12 miles long.
You can run 6 miles per hour and walk 3 miles per hour. Write and
graph an equation describing your possible running and walking
times on the fitness trail. Give three possible combinations of
running and walking times.
___x + ___y = 12
x- intercept
___x + ___(
) = 12
y- intercept
___( ) + ___y = 12
3 possibilities
August 18, 2012
At the start of a trip, you fill up your car's fuel tank with gas. After
you drive for x hours, the amount y (in gallons) of gas remaining is
given by the equation y = 18 – 2x.
a. Find the x-intercept and they-intercept of the given equation's
graph. Use the intercepts to graph the equation.
b. What real-life quantities do the x- and y-intercepts represent in this
situation?
c. After how many hours of driving do you have only 1/4 tank of gas
left?