Quadratic Equations

sapphire

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Apr 25, 2021
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Determine the equation, in factored form, of the parabola with roots at 4 and -6 that also passes through the point (1, -3).
 
 
If you could solve this problem correctly, you would understand many of the parabola's properties.

I would start by [MATH](x + a)(x + b) = 0[/MATH]
 
If a quadratic function has a zero at x= 4 then it has x- 4 as a factor. If it has a zero at x= -6 then it has x+ 6 as a factor. Since it is quadratic those are the only factors, involving x, that it has. It can have constant factor. What must that constant be so that when x= 1, y= -3?
 
Determine the equation, in factored form, of the parabola with roots at 4 and -6 that also passes through the point (1, -3).
If a quadratic has roots [MATH]x=\alpha[/MATH] and [MATH]x=\beta[/MATH], then it's equation is:
[MATH]y=a(x-\alpha)(x-\beta)[/MATH], for some constant '[MATH]a[/MATH]'
You know two roots; one can be [MATH]\alpha[/MATH], one [MATH]\beta[/MATH], so you can fill in most of the equation.
To find the final bit '[MATH]a[/MATH]', use the point you have: when [MATH]x=1, y=-3[/MATH].
 
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