Accelerated Evolution

# algebra help II

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"Is each question a direct variation? If it is, what is the constant of variation?"

y = 5 over 3 x

TT;; I don't get it at all..

Is it (5/3)x or 5/3x?

5/3x

It's been a while since I had Algebra, but that doesn't sound like direct variation to me.

TT...can someone tell me how to figure that out????

Well, direct variation would be something like y=mx, where m is a constant. That is to say, a change in y would result in a direct change in x. If that x had been on the outside, 5/3 would have been a constant. Even if you solve for x and determine y, y is still in a fraction. So, my vote goes to no.

whatt I don't get it at all..>>

OK, then think about the graph of the function. y=3x would produce a straight line. y=(5/3)x would also produce a straight line. y=5/3x would produce a parabolic function (or whatever the hell that double-curve thing in quadrants I and III is, someone besides Lindsay can tell me). Therefore, since the line isn't straight, the variation isn't direct.

like...

y = 2x + 4 and I know the answer is that it is not a direct variation (the back of the book says so) but how would I know?

you graph it, and see if the line is linear or not

how would I graph y = 2x + 4 ?

hmmm, y=2x+4 is a linear line... in which case it should be a direct variation.... unless it's the 4 that throws everything off...

I really don't know how to explain this, partly because i'm not sure myself.

Direct variation is when 2 variables, in your y=2x+1 example, they would be y and x, well.. it's when they have a constant ratio. Meaning.. as y changes, then x changes in proportion to y

Hmmm.. sorry, I don't think I can help, I haven't taken Algebra in a while.. Hope you could figure it out though

EDIT: After more thought, y=2x+4 should definitely be a direct variation... because 2 acts as the constant, and when y doubles (or tripes, or whatever) then so does x... What am I missing?

A direct variation equation has to pass through the origin (0,0). So y = 2x + 4 is not a direct variation because it does not passes through the origin, it pass through (0,4). A direct variation equation must be in the form of y = kx, where k is a constant. y = kx + b is not a direct variation.

Direct Variation follows the formula y = kx. Y is Y, X is X, and K is the variation constant.

y = 3x,

Direct Variation, K = 3

y = 3x + 2,

NOT Direct Variation

4y = 6x, y = 6x/4,

Direct Variation, K = 6/4 = 3/2 = 1.5

4y = 6x + 9, y = 6x/4 + 9/4,

NOT Direct Variation

Got it?

wait how do i solve this

y = 2x + 4 ??

wait how do i solve this

y = 2x + 4 ??

It is solved, for y. To solve it for a value, insert the value (i.e. for x=2, then it would be y=2(2)+4=8). To solve it for x, subtract the four from both sides and then divide both sides by 2. To graph it, plot a line with a slope of 2 which intersects the y-axis at y=4.

How do you convert slope intercept form (y = mx+b) to standard form?? (Ax + By = C)

also, what the hell????

"find the slope of a line parallel to the graph of each equation."

y = 1/2x + 2.3

How do you convert slope intercept form (y = mx+b) to standard form?? (Ax + By = C)

Man, that's ancient. I haven't seen 'standard form' in a long time. I don't even remember anymore.

also, what the hell????

"find the slope of a line parallel to the graph of each equation."

y = 1/2x + 2.3

Well, it seems to me that a line parallel to any graph would share it's slope. Maybe it's a trap!

Now I remember why I failed Algebra and took it over the summer Freshman year of HS.

woah guys, I actually figured out the paralell line thing ON MY OWN.

How do you convert slope intercept form (y = mx+b) to standard form?? (Ax + By = C)

Just get the x and y variables on the left side of the equation. For example, with the y = (1/2)x + 2.3 equation, all you would need to do is subtract the (1/2)x from both sides to give you -(1/2)x + y = 2.3. Remember that A, B, and C are just constants, so all you really have to worry about when getting an equation into standard form is getting both the x and the y on the left side of the equation. In that last example, A = -1/2, B = 1, and C = 2.3.

woah guys, I actually figured out the paralell line thing ON MY OWN.

...Ok, you deserve it.

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