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### Unit 3: Lesson 11

Extra practice: Intercepts

# x-intercept of a line

Sal determines the x-intercept of a linear equation from a graph. Afterwards, he checks his work by plugging values back into the equation. Created by Sal Khan.

## Want to join the conversation?

• How do you find the y intercept?
• You can take the function f(x) = something (your funtion) so like f(x)=2x. you can input x=0 and find the output which would be the y intercept. So, lets actually have f(x) = 5x + 2. You input 0 for x and you get f(x) = 2. That is your y intercept
• how to find x intercept when y= -x^2+16
• make y=0:
x^2=16 (I subtracted x^2 from both sides)
x=4 or -4 (two x-intercepts! this is because 4^2 is 16 and -4x-4 is ALSO 16)
• how would you find the x intercept of 2x-y= 5?
• To find any x-intercept, you use y=0 in the equation and calculate "x".
2x-0=5
Can you take it from here?
• I have a question what is the equation of x intercept?
• There is no equation. You take the linear equation that you have and you replace Y with 0. Then, solve for X. You will have a point on the line at (x-value, 0) where the x-value is the value you found. This point is where the line cross the x-axis (so, it is the x-intercept).
• b r e a d- what is the x-intercept of y=-240x+16-304?
• You can find the x-intercept by setting y=0
0=-240x+16-304
Then, solve for "x".
Hope this helps.
• Slope intercept form is y=mx+b.
Is there a way to use the x-intercept instead of the y-intercept. Use p for the y-intercept in your equation.

My attempt:
y = mx + b
0 = mx + b
0 = x + b/m
x = -b/m
let p be the x-intercept
therefore: p = -b/m
Therefore:y = mx - mp
Am I right?
• If m = 3 and b = 2 (Substitute) 0 = 3x + 2 (0 = mx + b) (Subtract b from both sides)
0-2 = 3x (y-b = mx) -2 = 3x (y-b = mx) (divide both sides by the amount x is multiplied by) -2/3 = x
• What is a slope?
• slope is basically change in y over change in x.the formula is (y1 - y2)/(x1 - x2)... where y1 and y2 are two different values of y and same for x respectively .
hope that helps
• At , why did he choose to do 2(0)? Did have to multiply by 0, or was that just a random number? Plz help!!
• The x-intercept is a point on the x-axis where the line crosses the x-axis. To find the x-intercept, you always use a value of y=0 because if y doesn't = 0, then the point will not be on the x-axis.

Hope this helps.
• how do you find x intercept
• The x-intercept of a line is where the line crosses the x-axis. It's coordinates will always be: (x-value, 0) because "y" must equal 0 for the point to be on the x-axis.

1) If you are given a graph of the line, you can estimate the x-intercept by find the coordinates of that point on the x-axis.
2) If you are given the equation of the line, then you can calculate the x-intercept by using y=0 in the equation to find the corresponding x-value.

Hope this helps.