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Which equation represents a parabola opening to the left with a vertex at the origin and a focus at (-7, 0)?

a. x=1/28 y^2
b. x= - 1/28 y^2
c. y= 1/20 x^s
d. y= - 1/20 x^s​

User Luan Si Ho
by
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1 Answer

4 votes

Answer:

b. x=1/28 y^2

Explanation:

the standard equation,


y^(2) = 4ax ---(1) , when opening towards left or right

focus at (a , 0)


x^(2) = 4ay ---(2) , when opening towards top or bottom

focus at (0, a)

if a is negative parabola will open toward negative axes ( down or left) and vice versa.

re- arranging option b. we get


y^(2) =28 x\\y^(2) = 4 X (-7 x) -----(3)

therefore, a = -7

(3) is similar to (1)

So it is facing left with focus at (-7,0)

User Bofredo
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