How do you solve the following system?: $-21x+3y=21 , -6x+3y=17$

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Answer 1 · 2015-11-29T00:40:30

$(-4/15 , 77/15)$

Given system of equation
$-21x+3y= 21 " " " " " " (1)$
$-6x+3y =17 " " " " " " (2)$

Multiply the first equation by $-1$

$-1 * (-21x+3y=21)$

$21x-3y=-21 " " " (3)$

Add equation $(2)$ from equation $(3)$

$21x-3y=-21$
$-6x+3y=17$
$stackrel("--------------------------------")$

$15x = -4$

$color(red)(x =- 4/15)$

Substitute $x=-4/15$ for $y$ in equation $(1)$

$-21*(-4/15) + 3y= 21$

$28/5 +3y =21$

$5(28/5+3y=21)$

$28+15y =105$

$15y= 77$

$color(red)(y = 77/15)$

How do you solve the following system?: -21x+3y=21 , -6x+3y=17 -21x+3y=21 , -6x+3y=17