Question

1/3 x− 1/8 y=3 7y+9x=−2 please solve the system 45 points for who does

Answer 1

Answer:

$x=6\\y=-8$

Step-by-step explanation:

$\frac{1}{3}x-\frac{1}{8}y=3\\ 7y+9x=-2$

One method could be rewriting the second equation as x in terms of y and solving by replacing in the first equation.

$7y+9x=-2\\9x=-2-7y\\x=\frac{-7y-2}{9}$

Replace...

$\frac{1}{3}x-\frac{1}{8}y=3$

$\frac{1}{3}(\frac{-7y-2}{9})-\frac{1}{8}y=3$

$\frac{-7y-2}{27}-\frac{1}{8}y=3$

$-\frac{7}{27}y-\frac{2}{27}-\frac{1}{8}y=3$

add $\frac{2}{27}$ on both sides.

$-\frac{7}{27}y-\frac{1}{8}y=3+\frac{2}{27}$

Combine like terms

$\frac{(-7)(8)-(1)(27)}{(27)(8)} y=\frac{(3)(27)+2}{27}$

$\frac{-56-27}{216} y=\frac{81+2}{27}$

$\frac{-83}{216}y =\frac{83}{27}$

Now, to get rid of the fraction and isolate y, multiply by the reciprocal or the inverted fraction.

$(\frac{216}{-83}) \frac{-83}{216}y =\frac{83}{27}(\frac{216}{-83})$

$y=\frac{216}{-27}$

Simplify

$y=-8$

Now replace the value of y in either equation to find x.

$7y+9x=-2\\7(-8)+9x=-2\\-56+9x=-2$

add 56

$56-56+9x=-2+56\\9x=54$

Divide by 9

$\frac{9x}{9}=\frac{54}{9}\\ x=6$

To check whether these values are accurate, replace in either equation both values and you should have an equality. In this case I'll do it in both equations.

$\frac{1}{3}x-\frac{1}{8}y=3$

$\frac{1}{3}(6)-\frac{1}{8}(-8)=3$

$2-(-1)=3\\2+1=3\\3=3$

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$7y+9x=-2\\7(-8)+9(6)=-2\\-56+54=-2\\-2=-2$