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Mathematics 24 Online
OpenStudy (howard-wolowitz):

ONE QUESTION! @=people

OpenStudy (howard-wolowitz):

@Michele_Laino

OpenStudy (michele_laino):

here we have to conjecture a linear relationship between y and x, namely: y=a*x+b x= elongation y= applied mass

OpenStudy (michele_laino):

using your data, we can write: \[\left\{ \begin{gathered} 70 = a \times 18 + b \hfill \\ 100 = a \times 24 + b \hfill \\ \end{gathered} \right.\]

OpenStudy (michele_laino):

we have to solve that system for "a" and "b"

OpenStudy (howard-wolowitz):

alright, solving for a and b

OpenStudy (michele_laino):

yes!

OpenStudy (michele_laino):

for example I solve the first equation for b, and I get: \[b = 70 - 18a\]

OpenStudy (michele_laino):

then I substitute that expression into the second equation, so I can write: \[100 = 24a + \left( {70 - 18a} \right)\]

OpenStudy (michele_laino):

what is a?

OpenStudy (howard-wolowitz):

actualy no

OpenStudy (michele_laino):

we have to simplify as below: \[100 = 24a + 70 - 18a\]

OpenStudy (howard-wolowitz):

ok one sec

OpenStudy (howard-wolowitz):

5

OpenStudy (michele_laino):

\[\begin{gathered} 100 = 70 + 6a \\ 100 - 70 = 6a \\ \end{gathered} \]

OpenStudy (howard-wolowitz):

ok one sec

OpenStudy (michele_laino):

ok! a= 5

OpenStudy (howard-wolowitz):

a=5 for both

OpenStudy (michele_laino):

now I substitute a=5 into the first equation, for example, so I get: \[\begin{gathered} 70 = 18 \times 5 + b \\ 70 = 90 + b \\ \end{gathered} \]

OpenStudy (michele_laino):

what is b?

OpenStudy (howard-wolowitz):

-20

OpenStudy (michele_laino):

ok! so our relationship is: y=5x-20

OpenStudy (howard-wolowitz):

you mean 1/5x

OpenStudy (howard-wolowitz):

ohh I see nvm sorry

OpenStudy (michele_laino):

no, y= 5x-20 I have made an error, when I wrote: x= elongation y= applied mass

OpenStudy (michele_laino):

nevertheless to get the right answer it is suffice to change x, y each other

OpenStudy (michele_laino):

so we can write: x=5y-20

OpenStudy (michele_laino):

then we can solve that equality for y, and we get this result: \[y = \frac{1}{5}x + 4\]

OpenStudy (michele_laino):

since your problem consider x as the applied weight and y the elongation produced by that weight

OpenStudy (michele_laino):

as you can see I have conjectured viceversa

OpenStudy (howard-wolowitz):

yes I get it

OpenStudy (michele_laino):

so, what is the right option?

OpenStudy (howard-wolowitz):

D?

OpenStudy (michele_laino):

yes!

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