How do you solve this system of equations using the substitution method $x - y = 4 and 6 x + 4 y = - 66$ $x- y = 4 and 6x + 4y = - 66$ ?

Question

2100 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2017-10-19T04:07:40

$y = - 9, x = - 5$ $y=-9, x=-5$

$x - y = 4 \Rightarrow$ $x-y=4 rArr$ equation 1
$6 x + 4 y = - 66 \Rightarrow$ $6x+4y=-66 rArr$ equation 2

Make either $x$ $x$ or $y$ $y$ the subject of equation 1, so you can substitute the values of in into equation 2.

$x = 4 + y$ $x=4+y$

Substitute this into equation 2.

$6 (4 + y) + 4 y = - 66$ $6(4+y)+4y=-66$
$24 + 6 y + 4 y = - 66$ $24+6y+4y=-66$
$10 y = - 90$ $10y=-90$
$:.y=-9$

To find $x$ , substitute $y=-9$ back into either equation 1 or 2.

$x-(-9)=4$
$x=4-9$
$:.x=-5$

How do you solve this system of equations using the substitution method x- y = 4 and 6x + 4y = - 66x−y=4and6x+4y=−66x- y = 4 and 6x + 4y = - 66?