The given function `y = 10/(x+7)-5 ` is the same as:
`y =10/(x+7)-5(x+7)/(x+7)`
`y=10/(x+7)-(5x+35)/(x+7)`
`y=(10-(5x+35))/(x+7)`
`y=(10-5x-35)/(x+7)`
`y = (-5x-25)/(x+7)`
To be able to graph the rational function `y = (-5x-25)/(x+7)` , we solve for possible asymptotes.
Vertical asymptote exists at `x=a` that will satisfy `D(x)=0` on a rational function `f(x)= (N(x))/(D(x))` . To solve for the vertical asymptote, we equate the expression at denominator side to 0 and solve for `x` .
In `y =(-5x-25)/(x+7)` , the `D(x)=x+7` .
Then, `D(x) =0 ` will be:
`x+7=0`
`x+7-7=0-7`
`x=-7`
The vertical asymptote exists at `x=-7` .
To determine the horizontal asymptote for a given function: `f(x) = (ax^n+...)/(bx^m+...)` , we follow the conditions:
when `n lt m ` horizontal asymptote: `y=0`
`n=m ` horizontal asymptote: ` y =a/b`
`ngtm` horizontal asymptote: NONE
In `y =(-5x-25)/(x+7)` , the leading terms are `ax^n=-5x or -5x^1` and `bx^m=x or 1x^1` . The values n =1 and m=1 satisfy the condition: `n=m` . Then, horizontal asymptote exists at `y=-5/1 or y =-5` .
To solve for possible y-intercept, we plug-in `x=0` and solve for `y` .
`y =(-5*0-25)/(0+7) `
`y =(-25)/7`
`y = -25/7 or -3.571 ` (approximated value)
Then, y-intercept is located at a point `(0, -3.571)` .
To solve for possible x-intercept, we plug-in `y=0` and solve for `x` .
`0 =(-5x-25)/(x+7)`
`0*(x+7) =(-5x-25)/(x+7)*(x+7)`
`0 =-5x-25 `
`0+5x=-5x-25+5x`
`5x=-25`
`(5x)/5=(-25)/5`
`x=-5`
Then, x-intercept is located at a point `(-5,0).`
Solve for additional points as needed to sketch the graph.
When `x=3,` the `y = (-5*3-25)/(3+7)=-40/10=-4.` point:` (3,-4)`
When ` x=-6` , the `y = (-5(-6)-25)/(-6+7)=5/1=5` . point: `(-6,5)`
When `x=-9` , the `y =(-5(-9)-25)/(-9+7)=20/(-2)=-10` . point: `(-9,-10)`
When `x=-12` , the `y = (-5(-12)-25)/(-12+7)=35/(-5)=-7` . point: `(-12,-7)`
As shown on the graph attached, the domain: `(-oo, -7)uu(-7,oo)` and range: `(-oo,-5)uu(-5,oo)` .
The domain of the function is based on the possible values of `x.` The `x=-7` excluded due to the vertical asymptote.
The range of the function is based on the possible values of `y` . The `y=-5` is excluded due to the horizontal asymptote.
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