- #1
Lo.Lee.Ta.
- 217
- 0
Finding the limit as x--> infinity: [sqrt(5 + 5x^2)]/(5 + 7x)
1. lim[√(5 + 5x^2)]/(5 +7x)
x→∞
2. Alright, I thought I would have first find the largest exponent of x in the denominator.
In this case, the largest exponent is x^1.
The next step is to divide every term by x^1.
Since I cannot divide something in a square root by x, I thought I COULD multiply it by
√(1/x^2). That's the same thing as dividing by x.
So, this is what I have:
[√(1/x^2)*√(5 + 5x^2)]/(5/x + 7x/x)
= [ √(5/(x^2) + 5x^2/x^2) / ((5/x) + 7) ] * (1/x^2)/(1/x)
= √((5/x^2) + 5) / ((5/x) + 7)
Then I thought if you substitute infinity for x here, then the (5/x^2) and the 5/x both equal 0.
So, it's √((5/0) + 5) / (0 + 7)
= √(5)/7
...This is not the right answer... =_=
Could you find my mistakes?
Thank you so much!
1. lim[√(5 + 5x^2)]/(5 +7x)
x→∞
2. Alright, I thought I would have first find the largest exponent of x in the denominator.
In this case, the largest exponent is x^1.
The next step is to divide every term by x^1.
Since I cannot divide something in a square root by x, I thought I COULD multiply it by
√(1/x^2). That's the same thing as dividing by x.
So, this is what I have:
[√(1/x^2)*√(5 + 5x^2)]/(5/x + 7x/x)
= [ √(5/(x^2) + 5x^2/x^2) / ((5/x) + 7) ] * (1/x^2)/(1/x)
= √((5/x^2) + 5) / ((5/x) + 7)
Then I thought if you substitute infinity for x here, then the (5/x^2) and the 5/x both equal 0.
So, it's √((5/0) + 5) / (0 + 7)
= √(5)/7
...This is not the right answer... =_=
Could you find my mistakes?
Thank you so much!