Why 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.
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1 lesson for “Variables on both sides”
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How does subtracting the equations remove a variable?
When both equations share a term like 2y, that term becomes your exit: subtract the equations and it disappears.
Try this lessonWhat do you add to make x^2 + 6x a perfect square?
A perfect square like (x + 3)^2 is easy to solve. Completing the square builds one on purpose, right in the middle of an equation.
Try this lessonWhat is sin A when the opposite side is 3 and the hypotenuse is 5?
Trigonometry begins with one idea: a ratio of two sides. Label the sides for your chosen angle, and the ratio is mechanical.
Try this lessonWhat is the opposite of adding 7?
Owen solved x + 7 = 12 by computing 12 + 7 = 19. He added again instead of undoing the addition.
Try this lessonWhy is 0.4 × 0.3 smaller than both?
Multiplying is supposed to make things bigger, and here it made something smaller. That is not a trick, it is what happens when both numbers are less than one.
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