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Mathematics 20 Online
klmjnmkj:

math problem

klmjnmkj:

1 attachment
klmjnmkj:

1 attachment
klmjnmkj:

@AZ

Florisalreadytaken:

\[ \begin{cases} 5x+7y=6 \\ -10x-14y=-12 \end{cases} \] we can see that we can multiply by negaive 2 the 1st equation; \[ \begin{cases} (5x+7y=6) \times 2 \\ -10x-14y=-12 \end{cases} \Rightarrow \begin{cases} -10x-14y=-12 \\ -10x-14y=-12 \end{cases} \] that said, we can understand that there will be 2 lines, but both of them will have the same position; so there will only be 1 line in the grap which means there are \( \infty\) solutions to that

klmjnmkj:

there isnt an infinite option

Florisalreadytaken:

oh, i thought it was a similar question to the previous one 🤦‍♂️

Florisalreadytaken:

\[ \begin{cases} 5x+7y=6 \\ -10x-14y=-12 \end{cases} \] this time ,we're solving for x \[ \begin{cases} 5x=6-7y \\ -10x-14y=-12 \end{cases} \Rightarrow \begin{cases} \cancel{5}x==\frac{6}{5}+\frac{-7 y}{5} \\ -10x-14y=-12 \end{cases} \] lets plug that value of x in the 2nd equation: \[ \begin{cases} -10\left(\frac{6}{5}-\frac{7 y}{5}\right)-14 y=-12 \\ \frac{6}{5}+\frac{-7 y}{5} \end{cases} \] remember \( a(b+c)=a b+a c \) ?? thus, \[ \begin{cases} -10\left(\frac{6}{5}\right)-10\left(-\frac{7 y}{5}\right)-14 y=-12 \\ \frac{6}{5}+\frac{-7 y}{5} \end{cases} \]

Florisalreadytaken:

so this is the part that we want to start simplifying \[ \begin{cases} \cancel5 \cdot\left(-2\left(\frac{6}{\cancel5}\right)\right)-10\left(-\frac{7 y}{5}\right)-14 y=-12 \\ \frac{6}{5}+\frac{-7 y}{5} \end{cases} \] by canceling that, we get: \[ \begin{cases} -2 \cdot 6-10\left(-\frac{7 y}{5}\right)-14 y=-12 \\ \frac{6}{5}+\frac{-7 y}{5} \end{cases} \]

Florisalreadytaken:

ok am lazy do to the latex so ill be explaining it -- so now we do \( -2 \cdot6 = -12 \) -- after that to get rid of the other denominator, my writing \( -10 \) in the form of \( -2 \cdot 5 \) after we cancel the 5ves as well we end up getting this : \[ \large \begin{cases} -12-2(-7 y)-14 y=-12 \\ \frac{6}{5}+\frac{-7 y}{5} \end{cases} \]

Florisalreadytaken:

multiply \( 2 \) and \( -7y \) \[ \begin{cases} -12+ 14y -14 y=-12 \\ \frac{6}{5}+\frac{-7 y}{5} \end{cases} \] \[ \ \ \ \ \ \ \ \ \Updownarrow \] \[ \begin{cases} -12=-12 \\ \frac{6}{5}+\frac{-7 y}{5} \end{cases} \] since we have \( -12=-12 \) , which is equal to \( 0=0 \) , it means that that statement will always be true that tells us that \( x = x \) -- so you can see even in the options, that we are writing \(x\) just as \(x \) lol what we should do now, is solve for y

Angee:

Substitute the x as a variable type it in in the calculator exactly like that then put (,x) at the and and it should give you the answer

Florisalreadytaken:

so yeah lets solve for \(y\) \[ \frac{6}{5}+\frac{-7 y}{5} \] \[ \ \ \ \ \ \ \ \ \ \Updownarrow \] \[ -\frac{7 y}{5}=x-\frac{6}{5} \] \[ \ \ \ \ \ \ \ \ \ \Updownarrow \] \[ -\frac{7 y}{5}=x-\frac{6}{5} \] \[ \ \ \ \ \ \ \ \ \ \Updownarrow \text{multiply both sides by} -\frac{7 y}{5} } \] \[ \frac{-5}{7} \cdot\left(-\frac{7 y}{5}\right)=-\frac{5}{7} \cdot\left(x-\frac{6}{5}\right) \] \[ \ \ \ \ \ \ \ \ \ \Updownarrow \text{factor 5 out of the negative 5 so we can calncel the 5ves} \] \[ \frac{\cancel 5 \cdot-1}{7} \cdot \frac{-7 y}{\cancel{5}}=-\frac{5}{7} \cdot\left(x-\frac{6}{5}\right) \] \[ \ \ \ \ \ \ \ \ \ \Updownarrow \] \[ \frac{-1}{7} \cdot(-7 y)=-\frac{5}{7} \cdot\left(x-\frac{6}{5}\right) \]lapsus*

Florisalreadytaken:

ugh nvm you can read it anyway

Florisalreadytaken:

wait, i just noticed -- were not finished with the left side yet, because we can siplify the \( \frac{number}{7} \) by factoring \(7\) out of \( -7 y \): \[\frac{-1}{\cancel { 7}} \cdot(\cancel{7}(-y))=-\frac{5}{7} \cdot\left(x-\frac{6}{5}\right) \] \[\ \ \ \ \ \ \ \ \ \Updownarrow\] \[ y=-\frac{5}{7} \cdot\left(x-\frac{6}{5}\right) \] and now were totally finished with the left side. i mean we got to y, where we want it to be

klmjnmkj:

so its B or the second option

Florisalreadytaken:

wait i havent finished it yet myself as im going with the same pace as my latex😹 -- i will skip this second part -- too lazy

Florisalreadytaken:

ok, so in the end we are going to have \( y= -\frac{5 x}{7}+\frac{6}{7} \) we said \( x=x \) that said, we would get something like: \[ \left(x, - \frac{5 x}{7} + \frac{6}{7}\right) \] which option is that?

Florisalreadytaken:

@klmjnmkj ??

klmjnmkj:

f or the last option

Florisalreadytaken:

yeah, that looks right

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