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ACT Math Videos 164 videos

ACT Math 1.1 Pre-Algebra
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Pre-Algebra Drill 1, Problem 1. Calculate 23 + 53(7 – 4).

ACT Math 1.1 Trigonometry
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ACT Math: Trigonometry Drill 1, Problem 1. What is the length of y?

ACT Math 1.2 Coordinate Geometry
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ACT Math: Coordinate Geometry Drill 1, Problem 2. Solve the inequality and determine which solution is shown on the number line.

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ACT Math 2.5 Coordinate Geometry 231 Views


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ACT Math: Coordinate Geometry Drill 2, Problem 5. What is the origin of the circle?

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Transcript

00:02

For a good time, solve this shmoopy question.

00:05

A circle has the equation (x - 3)2 + (y + 7)2 = 49.  What is it's origin?

00:13

And here are your potential answers...

00:17

Okay, so this is just testing to see if we know the standard formula for a circle.

00:21

The formula of a circle is the quantity x minus h squared plus the quantity y minus

00:26

k squared equals r squared, where (h, k) is the origin. Ok... so we want to find h and k...

00:32

And it looks like h is 3... and k is negative 7...Why?

00:37

Because two negatives make a positive 7 in the equation.

00:40

Our origin is (3, -7). Looks like our answer is C.

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