Why can't I add the x's to the plain numbers?
Lena simplified 5x + 3 + 2x + 4 and wrote 14x. She combined everything into x's, mixing apples with bananas.
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2 lessons for “Combining like terms”
What is (x + 3)(x + 5) expanded?
Every part of one binomial multiplies every part of the other. Four little products, then one tidy sum.
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Does doubling pressure double the volume?
Double the pressure and the volume halves; double the kelvin temperature and it doubles. Match each law to its direction.
Try this lessonWhat is the 20th term of 5, 9, 13, ...?
An arithmetic sequence changes by the same amount every time. With the formula, the 20th term is one calculation away.
Try this lessonWhat is the 5th term of 2, 6, 18, ...?
In a geometric sequence, each term multiplies the last by the same ratio. That ratio is the engine of the whole sequence.
Try this lessonWhat is (x^2 - 9)/(x^2 + 5x + 6) in lowest terms?
A fraction like this simplifies only after you factor the top and the bottom. Cancellation happens between factors, never between single terms.
Try this lessonWhy can't I just move the x?
Milo solved 3x + 2 = x + 10 by adding x to both sides: 4x = 12, so x = 3. Substitution showed 11 does not equal 13.
Try this lessonWhy does 18/24 turn into 3/4?
The fraction looks different and describes the same amount. The rule that allows this is the same rule that makes adding fractions possible at all.
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