Solve by substitution -2x+5y=-17 y=-4x+1
1 answer:
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<u>Step-by-step explanation:</u>
Since directrix is a horizontal line, this is a regular vertical parabola, where the x part is squared. The equation of a vertical parabola is:
(x - h)² = 4p(y - k)
where,
(h,k) are the coordinates of the vertex
p = distance from the vertex to the focus
So, we need to find out h, k and p and plug those values :
We know that the vertex of a parabola is halfway between focus and the directrix . We know the focus (0,4) and directrix y = 6 therefore, vertex (h,k) = (0, 0)
Now, p = distance from the vertex to the focus
= distance from the (0,0) to the (0,4)
= 4
Plug all the values in equation:
Now, we rearrange to write this into standard form (y =)
or,
check your calculator for the [!] factorial button.
also bear in mind that most calculators also have an [ₙPᵣ] button, to get Permuations, and you can just use that.