How do you solve $2 x + y = - 1$ $2x+y= -1$ and $- x + y = - 7$ $-x+y= -7$ using substitution?

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Answer 1 · 2018-07-02T04:06:54

$x = 2, y = - 5$ $color(magenta)(x = 2, y = -5$

$2 x + y = - 1 Eqn (1)$ $2x + y = -1 " Eqn (1)"$

$- x + y = - 7$ $-x + y = -7$

$x - y = 7 Eqn (2)$ $x - y = 7 " Eqn (2)"$

$1. Using elimination process$ $color(crimson)("1. Using elimination process"$

Adding Eqns (1) & (2),

$2x + x +cancel( y - y) = -1 + 7$

$3x = 6 " or " x = 2$

Substituting value of 'x' in Eqn (1),

$2*2 + y = -1$

$y = -1 + -4 = -5$

$color(crimson)("2. Using substitution process"$

$x = y + 7 " from Eqn (2)"$

Substituting value of 'x' in Eqn (1)",

$2 * (y + 7) + y = -1$

$3y = -1 -14 = -15$

$y = -5$

Substituting value of 'y ' in Eqn (2),

$x - (-5) = 7$

$x = 7 - 5 = 2$

How do you solve 2x+y= -1 2x+y=−12x+y= -1 and -x+y= -7−x+y=−7-x+y= -7 using substitution?