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ACT Math Pre-Algebra: Drill 3, Problem 4. Find the solution to this equation.
SAT Math 8.3 Algebra and Functions 204 Views
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Description:
SAT Math 8.3 Algebra and Functions
- Algebra and Functions / Systems of Linear Equations and Inequalities
- Product Type / SAT Math
- Algebra / Solve systems of equations
- Algebra / Solve systems of equations
- Algebra / Solve systems of equations
- Algebra / Solve systems of equations
- Heart of Algebra / Systems of linear equations in two variables (word problems)
Transcript
- 00:02
Here’s your shmoop du jour, brought to you by the difference of two squares.
- 00:06
Sure, all squares have their differences…but we hope these two can work things out.
- 00:12
If 9x2 - y2 = 15 and 3x - y = 3, what does 3x + y equal?
- 00:23
The most important thing is to recognize that, in this
- 00:25
problem, 9x squared minus y squared is a difference of two squares…
Full Transcript
- 00:33
…so “a squared minus b squared” can be factored into “a minus b times a plus b”.
- 00:41
9x squared is 3x times 3x.
- 00:43
So we can factor the first equation so it becomes (3x + y) times (3x - y) = 15.
- 00:50
Then we give a little whistle and call over the second equation…which we can now substitute:
- 00:55
(3x + y) times 3 = 15; then, dividing both sides by 3, we get 3x + y = 5.
- 01:01
So our correct answer is 5. Good boy. Now…roll over.
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