Calculating the foci (or focuses) of an Ellipse.

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### Linear Equations

00:07:38Salman KhanSolving linear equations with variable expressions in the denominators of fractions.

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### Another Percent Word Problem

00:06:18Salman KhanFinding the full price when you know the discount price.

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### Ratio Problem with Basic Algebra

00:05:12Salman KhanA slightly more involved ratio problem with algebra.

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### Alternate Solution to Ratio Problem

00:07:02Salman KhanAn alternate solution to the advanced ratio problem in the last video.

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### Complex Numbers Part 1

00:10:10Salman KhanIntroduction to complex numbers. Adding, subtracting and multiplying complex numbers.

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### Introduction to the Quadratic Equation

00:09:15Salman KhanIntroduction to using the quadratic equation to solve 2nd degree polynomials.

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### Quadratic Equation Part 2

00:09:14Salman Khan2 more examples of solving equations using the quadratic equation.

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### Functions Part 3

00:09:12Salman KhanEven more examples of function exercises. Introduction of a graph as definition of a function.

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### Proof: log a + log b = log ab

00:07:08Salman KhanProof of the logarithm property: log a + log b = log ab.

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### Proof: A(log B) = log (B^A), log A - log B = log (A/B)

00:07:57Salman KhanProofs of the logarithm properties: A(log B) = log (B^A) and log A - log B = log (A/B).

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### Introduction to Conic Sections

00:10:58Salman KhanWhat are conic sections and why are they called "conic sections"?

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### Parabola Focus and Directrix Part 1

00:14:31Salman KhanParabola as the locus of all points equidistant from a point and a line.

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### Parabola Focus and Directrix Part 2

00:18:28Salman KhanFinding the focus and directrix of a parabola.

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### Two Passing Bicycles Word Problem

00:05:39Salman KhanAlgebra word problem involving two bicycles passing each other.

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### Passed Bike Word Problem

00:05:54Salman KhanFun algebra word problem involving a train passing a bike.

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### Rational Inequalities Part 1

00:11:49Salman KhanTwo ways to solve a rational inequality (or an inequality involving a fractional expression).

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### Interesting Polynomial

00:16:15Salman KhanFinding the coefficients of a third degree polynomial given 2 roots and the y-intercept.

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### Geometric Series Sum to Figure Out Mortgage Payments

00:17:36Salman KhanFiguring out the formula for fixed mortgage payments using the sum of a geometric series.