Have questions about your preparation or an upcoming test? Need help modifying the Study Plan to meet your unique needs? No problem. Just book a Skype meeting with Brent to discuss these and any other questions you may have.

- Video Course
- Video Course Overview - READ FIRST
- General GMAT Strategies - 7 videos (all free)
- Data Sufficiency - 16 videos (all free)
- Arithmetic - 38 videos (some free)
- Powers and Roots - 36 videos (some free)
- Algebra and Equation Solving - 73 videos (some free)
- Word Problems - 48 videos (some free)
- Geometry - 42 videos (some free)
- Integer Properties - 38 videos (some free)
- Statistics - 20 videos (some free)
- Counting - 27 videos (some free)
- Probability - 23 videos (some free)
- Analytical Writing Assessment - 5 videos (all free)
- Reading Comprehension - 10 videos (all free)
- Critical Reasoning - 38 videos (some free)
- Sentence Correction - 70 videos (some free)
- Integrated Reasoning - 17 videos (some free)

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## Comment on

Total Number of Balls## to save some time and exempt

## Great approach!

Great approach!

## It seems like using

## Solving quadratic equations

Solving quadratic equations is an important skill to have on test day.

## hi Brent

When I'm solving a quadratic equation, why can't the answer be N=8 and N=-9 instead?

## You're right to say the

If you derived the equation N² - N - 72 = 0 , then the solutions cannot be 8 and -9.

We can verify this by plugging N = 8 and N = -9 into the equation.

For example, if N = 8, we get: 8² - 8 - 72 = 0

Simplify to get: -16 = 0. Doesn't work.

To solve the equation N² - N - 72 = 0 we must first...

Factor the left side to get: (N - 9)(N + 8) = 0

So, either N = 9 or N = -8

Does that help?

Cheers,

Brent

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