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a parabola curv have an equation as 3x + 1 = y^2 -y -1 which going through the y-axis in the positive side and also contain the smallest x value on the curv. Use quadratic equation to solve the point where the smallest x value is (coordinate).

 Jul 3, 2016
 #1
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a parabola curv have an equation as 3x + 1 = y^2 -y -1 which going through the y-axis in the positive side and also contain the smallest x value on the curv. Use quadratic equation to solve the point where the smallest x value is (coordinate).

 

The quadratic formula probably isn't necessary here....let's simplify the equation

 

3x + 1 = y^2 -y -1   subtract 1 from both sides

 

3x = y^2 - y - 2        divide both sides by 3

 

x = (1/3)y^2 - (1/3)y   - 2/3         complete the square on y   ....add 2/3 to both sides

 

x + 2/3 + 1/12  =  (1/3) (y^2  - y + 1/4)       factor the right side, simplify the left

 

(x + 3/4)  = (1/3) (y -1/2)^2         x takes on its minimum value at the  vertex which is    (-3/4, 1/2).....so x is minimum at -3/4

 

Here's the graph : https://www.desmos.com/calculator/j3plekvi77

 

 

cool cool cool

 Jul 3, 2016

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