Question

First I'd like to say I'm not a kid trying to get you to solve my homework. I've been out of scholl now for 20 years and its been a long time since I've done this stuff so be nice please.

Can I solve a 2 variable equation without having a set of equations. The actual problem is 120=20x + 4y?

Answer 1

yes and no .... yes, the equation can be solved for a specific variable "ex: solve for y" means get "y" by itself on one side of equation
no, you can't solve a single equation for a solution (a specific point) , because technically every point on the line would be a solution

Answer 2

i think you can. yu just need to subtitue the value of y in terms of x

Answer 3

substitute*

Answer 4

If you have two variables you need two equations to solve .. The same goes for a 3 variable equation: you need 3 equations.

Answer 5

i am in doubt

Answer 6

this works for anything . If you have two missing varialbes in a single equation like surface area , you need someway to relate one of those variables with what you're given

Answer 7

yes you can.., you just need to find the value of x and y that satisfies the equation..
since you just have one equation, then you'll have lots of solution for the equation...,

Answer 8

Well here's the thing I already know the answer x=5.77 and y=1.15 but how do you solve for x and y?

Answer 9

The original equation again was 120=20x+4y and as I said x=5.77 and y=1.15

Answer 10

in that case, you need a 2nd equation

Answer 11

x = 5.77 and y = 1.15 is one of the solutions if you have only one equation..,
how do you get these number? :)

Answer 12

Thats why I'm asking dont know?

Answer 13

I only found answer because I kept plugging in numbers til I found it. I had a diagram that gave this info. There is a torque of 120 inlbs on a 12 in base plate. I'm trying to solve for tension per bolt on the base there are 4 bolts and the bolts are 2 inches and 10 inches from the pivot. So to translate this into and equation you have 120= (x*10"*2bolts)+(y*2"*2bolts) there was a diagram that showed the 5.77 and 1.15 as the tensions per bolt and the explanation said a simple calculation can be done to find these answers?

Answer 14

Are you sure there aren't any other relationships between those numbers? Where are you reading this?

Answer 15

It is worth noting that the the ratio between those two numbers is very close to 5, which is also the ratio between the bolt distances from the pivot.

Answer 16

It's just the equation for a lever arm in action. As Archimedes said, give me a lever long enough and a fulcrum on which to place it and I'll move the Earth.

So you had two equations to solve:

\[120=20x + 4y\]\[x = (10/2)y = 5y\]As you have one already in terms of the other, I'd do substitution:\[120 = 20(5y) + 4y = 104y \rightarrow y = 120/104 = 15/13 \approx 1.15\]\[x =5(15/13) = 75/13 \approx 5.77\]

Answer 17

whpalmer.. sorry i logged off a bit ago. how did you arrive with the second equation? The x=(10/2)y=5y don't understand? and Thank you very much ahead of time

Answer 18

Also Im new to this site if i knew how I'd give you a medal

Answer 19

The lever formula is just the force = the lever arm * weight. Think of a see-saw.

If the pivot (fulcrum) is at r = 0, you've got one force pushing at r = 2" and another at r = 10". The force due to the one at 10" is (10/2) times the one at 2" because the lever arm is longer. Same idea as putting a piece of pipe over a wrench handle when you've got a bolt that won't move.

Answer 20

Thanks you are very smart and it's greatly appreciated. I never thought of thinking in those terms. You definitely got some good answers.