x + 2y - z = 9 2x + y + z = 3 3x - y + z = -2 berapakah nilai 2x+y-z?

<p>Jawaban yang tepat adalah 7</p><p>&nbsp;</p><p>Pembahasan :</p><p>x + 2y - z = 9 &nbsp; &nbsp; &nbsp; &nbsp;(1)<br>2x + y + z = 3 &nbsp; &nbsp; &nbsp; (2)<br>3x - y + z = -2 &nbsp; &nbsp; &nbsp; (3)</p><p>&nbsp;</p><p>Eliminasi z dari (1) dan (2)</p><p>x + 2y - z = 9<br><u>2x + y + z = 3</u> +</p><p>3x + 3y = 12 &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;</p><p>x + y = 4 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; (4)</p><p>&nbsp;</p><p>Eliminasi z dari (2) dan (3)</p><p>2x + y + z = 3<br><u>3x - y + z = -2</u> _</p><p>-x + 2y = 5 &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; (5)</p><p>&nbsp;</p><p>Eliminasi x dari (4) dan (5)</p><p>x &nbsp;+ &nbsp;y &nbsp;= 4&nbsp;<br><u>-x + 2y = 5 &nbsp;</u> +</p><p>&nbsp; &nbsp; &nbsp; &nbsp; 3y = 9</p><p>&nbsp; &nbsp; &nbsp; &nbsp; y = 3</p><p>&nbsp;</p><p>Substitusikan y = 3 ke persamaan (4)</p><p>x + y = 4</p><p>x + 3 = 4</p><p>x = 4 - 3</p><p>x = 1</p><p>&nbsp;</p><p>Sunstitusikan x = 1 dan y = 3 ke persamaan (1)</p><p>x + 2y - z = 9</p><p>1 + 2(3) - z = 9</p><p>1 + 6 - z = 9</p><p>7 - z = 9</p><p>-z = 9 - 7</p><p>-z = 2</p><p>z = -2</p><p>&nbsp;</p><p>Nilai 2x + y - z = 2(1) + 3 - (-2)</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 2 + 3 + 2</p><p>&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;= 7</p>