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Post by pteriforever on Mar 1, 2009 5:12:03 GMT -5
How to factorise a general quadratic trinomial of the form
ax^2 + bx + c
example:
4x^2 + 8x + 3
on one side, you put factors of the first term, 4x^2. Lets take 2x and 2x, and put these on one side of a cross.
2x`` ``X 2x``
on the other side, put factors of the third term, 3. 3 and 1 is the only combination. Put these on the other side of the cross.
2x``3 ``X 2x``1
multiply the terms on opposite sides of the cross and write them down.
2x``3 6x ``X 2x``3 2x
Add these together.
2x``3 6x ``X 2x``1 2x
`````8x
Although it is not so in this example, if the sum of these two numbers are not identical to the second term, retry with different factors. Negative factors are often needed.
In this example, however it does add up to the second term, 8x. This is then factorised easily, by adding together the two upper numbers of the cross and the two lower numbers. This gives
2x+3 and 2x+1
put these in brackets and multiply together to give the fully factorised form. (That was rather alliterative, wasn't it?)
(2x+3)(2x+1)
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Post by || allie on Mar 1, 2009 11:03:04 GMT -5
... O.O;
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Post by rose on Mar 1, 2009 11:06:39 GMT -5
Why is there a board for this?
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Post by hostlietakeover on Mar 1, 2009 12:11:12 GMT -5
Well, the good thing is I now have finished my Algebra homework! Rose has a point though...Why is this here?
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Post by pteriforever on Mar 1, 2009 15:48:59 GMT -5
Well, there's one for comma splices, isn't there?
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Post by Ten on Mar 1, 2009 16:35:21 GMT -5
It took me a while to figure out what you were explaining because you made it way more complicated than it has to be.
Well, there's one for comma splices, isn't there?
That's because I told Poizuun she needed a comma splice in her character's profile.
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Post by jenn on Mar 12, 2009 6:00:54 GMT -5
Reminds me of Pythagram Theorem... Or however you spell it. Whatever you call the a^2+b^2=c^2. Or, if you don't know "a" or "b", it's a^2-b^2=c^2. It's the formula to find the missing measures of right triangles. Could tell you the formulas to find areas of most quadrilaterals, triangles, and circles.
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Post by pteriforever on Mar 15, 2009 18:02:12 GMT -5
square: a^2
trapezium: h(a+b)/2
any triangle: ah/2
circle: Pi/4 * d^2
volume of sphere: Pi/6 * d^3
volume of cylinder: Pi/4 * d^2 * h
volume of triangle-based pyramid: abh/3
volume of square-based pyramid: (a^2 h)/3
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Post by jenn on Mar 17, 2009 19:31:37 GMT -5
I only know 2-D shapes area formulas. I've had to memorize them. The ones I can think of right now (I have a migraine, so my memory isn't that good right now): Triangle: B+H/2 Square: W^2 Rectangle: L*W Parallelogram: B*H Trapezoid: (B1+B2) Circle: Pi*R^2 Semicircle: Pi*R^2/2
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Post by [.___Paije] ! on Mar 17, 2009 20:25:03 GMT -5
Trapezoid: (B1+B2) -x- Divided by two. o3o
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