# How do you solve y= -x and y= x+9?

##### 1 Answer

Apr 30, 2018

#### Explanation:

#y=-xto(1)#

#y=x+9to(2)#

#"since both equations express y in terms of x we can"#

#"equate the right sides"#

#rArrx+9=-x#

#"add "x" to both sides"#

#x+x+9=cancel(-x)cancel(+x)#

#rArr2x+9=0#

#"subtract 9 from both sides"#

#rArr2x=-9#

#"divide both sides by 2"#

#(cancel(2) x)/cancel(2)=(-9)/2#

#rArrx=-9/2#

#"substitute "x=-9/2" into equation "(1)#

#rArry=-(-9/2)=9/2#

#"the point of intersection "=(-9/2,9/2)#

graph{(y+x)(y-x-9)((x+9/2)^2+(y-9/2)^2-0.04)=0 [-10, 10, -5, 5]}