Question

utilizando o método mais conveniente determine a solução de cada um dos seguintes sistemas de equação
$(x + y = 20) \\ (x - y = 8)$
$(3x -y = 18) \\ (x + y = 10)$


$(2x + y = - 3 ) \\ (x - 3y = - 26)$
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Answer 1

Explicação passo a passo:

$(x + y = 20)\\(x - y = 8)+\\-------\\2x= 28\\x = \frac{28}{2}\\x = 14\\\\\\x+y = 20\\14 + y = 20\\y = 20 - 14\\y = 6\\\\S = \{14\ ,\ 6\}\\\\\\\\\ \ (3x - y = 18)\\(x + y = 10) +\\-------\\4x = 28\\x = \frac{28}{4}\\x = 7\\\\\\x+y=10\\7+y=10\\y = 10 - 7\\y = 3\\\\S = \{7\ ,\ 3\}\\\\\\\\2x+y = -3\\y = -3 - 2x\\x - 3y = -26\\x - 3(-3-2x) = -26\\x +9+6x=-26\\7x=-26+9\\x=\frac{-17}{7}\\\\y = -3-2(\frac{17}{7})\\y = -3-\frac{34}{7}\\y = \frac{-63 - 102}{21}$

$y = \frac{-36}{21}\\\\\\S = \{-17/7\ , -36/21\}$