Mohon bantuannya,,,,,,,,,

Mohon bantuannya,,,,,,,,,

Jawab:

Penjelasan dengan langkah-langkah:

$displaystyle begin{aligned} left { dfrac{2}{x}+dfrac{1}{y} = 1} atop { dfrac{1}{x}-dfrac{2}{y} = 8}} right. end{aligned}to left[begin{array}{cc|c}2&1&1\1&-2&8end{array}right]$

$left[begin{array}{cc|c}2&1&1\1&-2&8end{array}right] xrightarrow{textstyle 1) B_1-B_2to B_1, 2) B_2-B_1to B_2} left[begin{array}{cc|c}1&3&-7\0&-5&15end{array}right] \\ left[begin{array}{cc|c}1&3&-7\0&-5&15end{array}right] xrightarrow{textstyle 1) dfrac{5B_1+3B_2}{5}to B_1, 2) dfrac{B_2}{-5}to B_2} left[begin{array}{cc|c}1&0&2\0&1&-3end{array}right]$

$left[begin{array}{cc|c}1&0&2\0&1&-3end{array}right] xrightarrow{textstyle 1) dfrac{1}{B_1}to B_1, 2) dfrac{1}{B_2}to B_2} left[begin{array}{cc|c}1&0&tfrac{1}{2} \0&1&-tfrac{1}{3}end{array}right]$

$x = dfrac{1}{2}, y = -dfrac{1}{3}\\x+y = dfrac{1}{6}\to boxed{boxed{dfrac{1}{x+y} = 6 }}$

Jawaban:

C. 4

Penjelasan dengan langkah-langkah:

x – 3y = -1 x = -1 + 3y

-5x + 2y = -8

-5(-1 + 3y) + 2y = -8

5 + (-15y) + 2y = -8

5 + (-13y) = -8

-13y = -8 -5

-13y = -13

y = 1

x = -1 + 3y

= -1 + 3(1)

= -1 + 3

x = 2

5x – 6y = 5(2) – 6(1) = 4

Jawaban : C. 4