slope equation help

Quadratic equations and inequalities, variation equations, function notation, systems of equations, etc.
will82abn
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Joined: Fri Feb 06, 2009 4:29 am
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slope equation help

problem y=-1/2(x+2)
in a problem like this one i understand it until the end. Through (5,-2) with slope -1/2. i know how to set it up, the part i am missing out on is the fraction at the end like y=-1/2x+1/2 how do you get the last part the 1/2, i know its easy but i am missing. Thanks so much anyone RCW

stapel_eliz
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Joined: Mon Dec 08, 2008 4:22 pm
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will82abn wrote:problem y=-1/2(x+2)
in a problem like this one i understand it until the end. Through (5,-2) with slope -1/2. i know how to set it up, the part i am missing out on is the fraction at the end like y=-1/2x+1/2 how do you get the last part the 1/2

How did you arrive at your answer? For instance, if you plugged the slope and the point into the point-slope formula so you had:

. . . . .y + 2 = -(1/2)(x - 5)

...by what steps did you arrive at "y = -(1/2)x + 1/2"?

stapel_eliz
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Joined: Mon Dec 08, 2008 4:22 pm
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In a private message, will82abn wrote:i am having problems with x1 not able or just don't see how to get the fraction at the end here is another problem y+3=3/4(x-2) then the problem begin when you dist the fraction 3/4 through to get 3/4x - 9/2 how to get the 9/2 is my prob.

Um... If I may venture to suggest, using standard capitalization, punctuation, and grammar might help explain your meaning (along with showing your steps)...?

I think you are saying (in the above quote) that you don't know how to work with fractions, so you don't understand how to multiply 3/4 and 2, and then to subtract 3, to end up with 9/2.

If you just need a little reminder of how to work with fractions, you could try studying this review. Otherwise, please take a break from what you're doing, and dedicate a few days or weeks to learning this topic. There are loads of great lessons available online, but the material can take a good while to absorb.

. . . . .Google results for "fractions"
. . . . .Google results for "simplifying fractions"
. . . . .Google results for "multiplying fractions"
. . . . .Google results for "dividing fractions"
. . . . .Google results for "least common multiple"
. . . . .Google results for "lowest common denominator"
. . . . .Google results for "mixed numbers fractions convert"

DAiv
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Joined: Tue Dec 16, 2008 7:47 pm
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Re:

will82abn wrote:i am having problems with x1 not able or just don't see how to get the fraction at the end here is another problem y+3=3/4(x-2) then the problem begin when you dist the fraction 3/4 through to get 3/4x - 9/2 how to get the 9/2 is my prob.

I find it easier to learn with examples to hand, so I'll lay it out, step by step, and hopefully, you may be able to see the pattern.

$y \,+\, 3 \,=\, \frac34(x \,-\, 2)$

Distribute the $\frac34$ through the parentheses:

$y \,+\, 3 \,=\, \frac34(x) \,-\, \frac34(2) \,\,\,$ , taking care with the minus sign.

Clean up:

$y \,+\, 3 \,=\, \frac34x \,-\, \frac64$

$y \,+\, 3 \,=\, \frac34x \,-\, \frac32$

To isolate the $y$, so it's on its own, subtract 3 from both sides:

$y \,+\, 3 \,-\, 3 \,=\, \frac34x \,-\, \frac32 \,-\, 3$

Clean up:

$y \,=\, \frac34x \,-\, \frac32 \,-\, 3$

Now, in order to combine the $-\frac32$ with the $-3$, both numbers need to be in the form of a fraction with the same denominator (the number on the bottom). The simplest way to do that here is to convert the -3 into a fraction with a denominator of 2. We do that by multiplying it by $\frac22$; this won't change the value, because any number divided by itself is 1, any number multiplied by 1 remains unchanged:

$y \,=\, \frac34x \,-\, \frac32 \,-\, 3 (\frac22)$

Clean up:

$y \,=\, \frac34x \,-\, \frac32 \,-\, \frac62$

Now we can combine the two fractions:

$y \,=\, \frac34x \,-\, \frac92$

If you can't see how $-\frac32 \,-\, \frac62 \,=\, -\frac92$

... you can rearrange the fractions like this:

$-\frac32 \,-\, \frac62 \,=\, \frac{(-3 \,-\, 6)}2 \,=\, \frac{(-9)}2 \,=\, -\frac92$

We just need to be careful with the minus signs.

DAiv

will82abn
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Joined: Fri Feb 06, 2009 4:29 am
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Re: slope equation help

Thanks DAvi, that was a great help, sorry if my standard capitalization, punctuation, and grammar was not up to par, first time user of this site. I knew it was somthing simple I was overlooking, but you nailed it thanks again. RCW