How to

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How to

  1. 1. “How To” Graphing In Vertex Form <br />Collin Kreisle.<br />
  2. 2. Equation: y=3x^2+6x+4<br />First you have to find the y-intercept. To find the y-intercept you always look at the number without an x attached to it. So in this example the “4” would be the y intercept. (0,4)<br />
  3. 3. Second:<br />The second thing you have to do is find the vertex. To find the vertex, you have to set up an equation . <br />Y= -3(X^2-2x+?)+4-?*-3<br />We left the two numbers as a question mark because we have to find them. The first blank is always left positive, while the other is always left as negative.<br />Next you take the number in parentheses, multiply it by half and then square it. <br />
  4. 4. Cont.<br />So our number with the x would be -2. <br />-2*1/2=-1^2=-1<br />This gives us our “Axis of symmetry”<br />Also it gives us the number that fills both of our blanks which is one.<br />
  5. 5. Third:<br />Next after you have found the remaining blanks you work the equation out. <br />This gives you y=-3(x-1)^2=7.<br />The seven gives us the other part of our vertex, which would make our vertex (1,7)<br />
  6. 6. Fourth: <br />The fourth step is to find the x-intercepts. <br />To find this we have to do the quatdratic formula. Y=-b+/ √ (-b)^2-4ac <br /> 2a<br />Next you have to know what you’re a, b, and c are. <br />To find them you have to go back to the original equation. Which is y=3x^2+6x+4.<br />
  7. 7. Cont.<br />So knowing that, the a comes from the number with x^2. B comes from the number with just the x, and c comes from the number by itself.<br />So if you filled in the equation with the correct numbers it would read –(6)+/- √ (6)^2-4(-3)(4) <br /> 2(-3)<br />-6+ √ 84= -.53-6- √ 84=2.53<br /> -6 -6<br />This would give you your x-intercepts of (-.53,0) and (2.53,0)<br />
  8. 8. Last:<br />The last thing to do would be graphing your points and creating your parabola. <br />

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