Big Ideas Math Algebra 2, 2014
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Big Ideas Math Algebra 2, 2014 View details
4. Adding and Subtracting Rational Expressions
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Exercise 57 Page 390

Find the pattern between consecutive terms in the given sequence.

Fourth term: 1+1/2+1/2+1/2+1/2+1/2 Fifth term: 1+1/2+1/2+1/2+1/2+1/2+1/2 Simplified terms:

Term Value
First 1.4
Second About 1.4167
Third About 1.4138
Fourth About 1.4143
Fifth About 1.4142

Limiting value: sqrt(2)

Practice makes perfect
Let's analyze the first two terms of the given sequence. 1+1/2+ 1/2, 1+1/2+ 1/2+1/2 Notice that the fraction 12 is changed to the expression 1/(2+ 12). Next, analyze the second and the third terms of the sequence.

1+1/2+1/2+ 1/2, 1+1/2+1/2+ 1/2+1/2 Fortunately, we have the same behavior as before. Therefore in the next terms of the sequence we should change the fraction 12 to 1/(2+ 12). Let's write the fourth and fifth term of the sequence! Fourth: 1+1/2+1/2+1/2+ 1/2+1/2 Fifth: 1+1/2+1/2+1/2+1/2+ 1/2+1/2

Simplified Terms

Next, using a calculator we can get the simplified terms of the given sequence.

Term Value
First 1.4
Second About 1.4167
Third About 1.4138
Fourth About 1.4143
Fifth About 1.4142

Limiting value

Since sqrt(2)≈ 1.414213..., it appears that the sequence approaches the value of sqrt(2).

Extra

Alternative way of finding the limiting value
We will justify more precisely that indeed our sequence should converge to sqrt(2). Since every next term in the sequence is created by replacing 12 by the expression 1/(2+ 12), the limiting value (x) should be in the following form. x=1+1/2+1/2+1/2+1/2+1/2+... Next, let's transform the expression in the following way. x=1+1/2+1/2+1/2+1/2+1/2+... x=1+1/1+1+1/2+1/2+1/2+1/2+... Notice that, in the part of the denominator we also get the expression x! x=1+1/1+1+1/2+1/2+1/2+1/2+... x=1+1/1+x Now, we will solve the last equation to find the value of x.
x=1+1/1+x
Solve for x
x(1+x)=1(1+x)+1
x+x^2=1+x+1
x^2=1+1
x^2=2
x=±sqrt(2)
Since x must be positive, it should be equal to sqrt(2). Therefore, the limiting value of the given sequence should be equal to sqrt(2).