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X-Intercept(s)
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In quadratic equations, we can have 0,1, or 2 x-intercepts. To find the x-intercepts we can use a special formula.
Recall that an x-intercept is where the line passes the x-axis.
Quadratic Formula
To find the x-intercepts we use the quadratic formula.
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If you notice the equation, you will see that the variables a,b, and c are in the quadratic formula. Those variables correspond with the coefficents in the standard equation.
Let's try a few examples of the quadratic formula.
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Standard Form
a,b, and c
Formula
a = 1
b = 4
c = 3
a = 1
b = 0
c = -9
a = 2
b = 3
c = -20
x-intercept(s)
-3 and -1
-4 and 2.5
-3 and 3
When doing the quadratic formula, if the square root value results in a negative number on the inside you will not have any x-intercepts.
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You can not take the square root of a negative number.
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The video below will demonstrate how to use the quadratic formula.
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Let's try an activity!
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Here is a Desmos activity!
*Once you finish the Desmos activity close out of the Desmos window
Class Code:
​6X8W43
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Click on the assessment button below the text to see what you retained about x-intercepts.
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If you did well on the assessment click the button below to go to the next objective (Vertex).
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