3 years ago

Do you guys know ? i really need helpp .

Mathematics

1 answer:

andrey2020 [161]3 years ago

3 0

Answer:

the first one

Step-by-step explanation:

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Solve the system of equations -3x+7y=-18 and 4x-4y=8 by combining the equations.

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Answer:

$\huge \colorbox{red}{(x,y)=(-1,-3)}$

Step-by-step explanation:

multiply first equation by 4 and second by 3 respectively:

$\begin{cases} \displaystyle - 12x + 28y = - 72 \\ \: \: \displaystyle \: 12x - 12y = 24 \end{cases}$

combine the equations:

$\underline{ \begin{cases} \displaystyle - 12x + 28y = - 72 \\ \: \: \displaystyle \: 12x - 12y = 24 \end{cases}} \\ \displaystyle16y = - 48$

divide both sides by -48:

$\displaystyle \: \frac{16y}{16} = \frac{ - 48}{16} \\ y = - 3$

substitute the value of y to the second equation

$\displaystyle \: 4x - 4. - 3 = 8$

simplify multiplication:

$\displaystyle \: 4x + 12 = 8$

cancel 12 from both sides:

$\displaystyle \: 4x = - 4$

divide both sides by 4

$\displaystyle \: \frac{4x}{4} = \frac{ - 4}{4} \\ x = - 1$

therefore our solution is

$\displaystyle (x,y)=(-1,-3)$

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Step-by-step explanation:

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