How would you find the domain of each: #y=(3x+2)/(4x+1)#? #y=(x^2-4)/(2x+4)#? #y=(x^2-5x-6)/(x^2+3x+18)#? #y=(2^(2-x))/(x)#? #y=sqrt(x-3)-sqrt(x+3)#? #y=sqrt(2x-9)/(2x+9)#?
2 Answers
The domain would be all real numbers except for any value of
Explanation:
For example, we can look at your first statement,
Any value of
To find what that value is, you can set up an equation like this:
After solving this, you would get the answer of
You would do the same for the other fraction problems. In the second problem, you would need to factor the denominator or use the quadratic formula to find the non-domain values.
For your square root problems, the domain would be any value of
For example, let's look at
We can set up our equations again:
The answers here would be
This means that any value of
The last question is an amalgam of these two problem types:
We can set up equations here again:
So anything less than
I hope that makes sense and helps you solve the fraction problems that I did not address.
Please see below.
Explanation:
Domain in
For example if we have
In case we have a quadratic polynomial such as
Sometimes factors may cancel out, if they are common between numerator and denominator. In that case, we call it a hole, because though
- In
#y=(3x+2)/(4x+1)# , domain isall#x# other than#x=-1/4# , as latter makes denominator#0# . - In
#y=(x^2-4)/(2x+4)=((x+2)(x-2))/(2(x+2))=(x-2)/2# and we cannot have#x=+-2# and domain is values of#x# other than#+-2# and at#x=2# , we have a hole. - As
#y=(x^2-5x-6)/(x^2+3x+18)=((x-6)(x+1))/((x+3/2)^2+63/4)# . Note that least value of denominator is#63/4# and hence#y=f(x)# exists for all vales of#x# and hence domain is#RR# . - In
#y=2^(2-x)/x# , we have no restrictions on#x# as far as numerator is concerned, however, denominator restricts domain of#x# so that#x!=0# . - In
#y=sqrt(x-3)-sqrt(x+3)# , as we have#sqrt(x-3)# we cannot have#x<3# and as we also have#sqrt(x+3)# , other restriction is we cannot have#x<-3# . This means domain is#x>=3# . - As
#y=sqrt(2x-9)/(2x+9)# , numerator places a restriction that#x>=9/2# and denominator#x!=-9/2# . This can be combined and domain is#x>=9/2# .