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CAHSEE Math 5.3 Algebra I 197 Views
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Description:
CAHSEE Math: Algebra I Drill 5, Problem 3. Which of the following graphs represents the solution to the following system of equations?
Transcript
- 00:03
Can you hear the people shmoop?
- 00:05
Which of the following graphs represents the solution to the following system of equations:
- 00:10
And here are the potential answers…
- 00:17
Okay, so to solve this problem, we basically need to figure out what the lines would look
- 00:21
like that are represented by this system of equations…
Full Transcript
- 00:24
…and then use the eyeball test to match it up with its twin.
- 00:27
Okay, so first we need to find the point of intersection of the lines.
- 00:31
What x value and y value will work for both?
- 00:34
If we multiply the first equation by -2… we’ll get -2x… meaning we can add it to
- 00:39
the bottom equation and be left with a single variable.
- 00:43
-2x – 2y = -4… plus 2x + 3y = 3…
- 00:49
…gives us y = -1.
- 00:51
Plugging that back into the first equation, we get an x value of 3.
- 00:55
So our point where these two lines get up close and personal? (3, -1)
- 01:00
That’ll rule out C and D, which both have different points of intersection. So long, fellas.
- 01:05
So we’re down to A and B…
- 01:06
We can figure out which one to nix by putting both of the given formulas into slope-intercept form...
- 01:12
The first one becomes y = -x + 2 and the second becomes y = -2/3x + 1…which tells us that
- 01:21
we’re dealing with two negative slopes.
- 01:23
Only B fits the bill.
- 01:24
As in, “Bicycle built for two.”
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