Answer:
c
Step-by-step explanation:
Answer:
32.59 (nearest hundredth)
Step-by-step explanation:
<u />
<u>Geometric sequence</u>
General form of a geometric sequence: 
(where a is the first term and r is the common ratio)
Given:
Therefore:
<u>Sum of the first n terms of a geometric series</u>:
To find the sum of the first 20 terms, substitute the found values of a and r, together with n = 20, into the formula:
To answer your question: Rewrite <span>81<span>x2</span></span> as <span><span>(<span>9x</span>)</span>2</span>.<span><span><span>(<span>9x</span>)</span>2</span><span>−49</span></span>Rewrite 49 as <span>72</span>.<span><span><span>(<span>9x</span>)</span>2</span><span>−<span>72</span></span></span> Both terms are perfect squares, factor using the difference of squares formula, <span><span><span>a2</span><span>−<span>b2</span></span></span>=<span><span>(<span>a+b</span>)</span><span>(<span>a<span>−b</span></span>)</span></span></span> where <span>a=<span>9x</span></span> and <span>b=7</span>.<span><span>(<span><span>9x</span>+7</span>)</span><span>(<span><span>9x</span><span>−7</span></span><span>)</span></span></span>
0.000044, because 10 to the negative fith is 0.00001, and 0.0001 times 4.4 is 0.000044
