Explained: "Solve {2x+3y=−16x+3y=−9"

postillan4

Answered question

2020-12-22

Solve ${\begin{cases} 2 x + 3 y = - 1 \\ 6 x + 3 y = - 9 \end{cases}$

FieniChoonin

Skilled2020-12-23Added 102 answers

${\begin{cases} 2 x + 3 y = - 1 \\ 6 x + 3 y = - 9 \end{cases}$

Solve equation (2) for y

$3 y = - 6 x - 9 y = \frac{- 6 x - 9}{3} y = - 2 x - 3$

Substitute equation (3) into equation (1) and solve for x

$2 x + 3 (- 2 x - 3) = - 1 2 x - 6 x - 9 = - 1 - 4 x - 9 = - 1 - 4 x = - 1 + 9 - 4 x = 8 x = - 2$

Substitute x = -2 into equation (3) and solve for y

$y = - 2 (- 2) - 3 y = 4 - 3 y = 1$

The solution is (-2, 1)

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