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ACT Math 3.1 Coordinate Geometry 501 Views


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ACT Math: Coordinate Geometry Drill 3, Problem 1. What shape is shown by the equation in this video?

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Transcript

00:02

And here is your shmoop du jour...

00:04

What shape is shown by the equation X -4 equals the quantity y plus 2 squared?

00:10

And here are the potential answers...

00:14

The key to this problem is knowing the standard equations of all of the

00:17

context in the list

00:19

First we can eliminate C, triangle from our options, because a

00:23

triangle cannot be shown by one equation

00:26

it's made up of three lines. Alright let's move back to A

00:29

Circle, the standard formula of a circle is

00:33

R-squared equals quantity X minus H squared plus quantity Y minus K

00:38

squared where R is the radius

00:40

HK is the center of the circle

00:43

The circle formula has X and Y radius to the second power

00:47

but our equation only raises one variable Y

00:50

to the second power. So we can cross A off our list.

00:53

Next up B. Ellipse, while the formula

00:57

of an ellipse is quantity X minus H square divided by

01:00

A squared plus quantity Y minus K squared

01:03

divided by B squared equals one where HK is the center

01:07

and A is half the length of the major axis

01:10

and B is half of the minor axis...well

01:14

does that look like our equation? No! Cross off B.

01:18

Next up, D, Parabola.

01:20

The equation of an up or down parabola

01:24

is Y minus K equals quanitiy

01:27

X minus H squared. Does that look like our equation? Well...

01:32

...Close but not quite, but wait what about those

01:36

sideways parabolas? Well the equation of a sideways parabola is

01:39

X minus H equals quantity Y minus K squared

01:44

and our equation is X minus 4 equals quanity Y plus 2 squared

01:47

Is that a match? Yeah! In our sideways parabola

01:51

H is 4 and K is negative 2. Got our answer.

01:55

D...Parabola

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