Let's assume the laptop is opened at 90 degrees (this is done for the sake of simplicity, is actually irrelevant) then each plane would be analogous to the 'x' and 'y' planes you see in a Cartesian Plane, which only intersect at one point called the Origin. Any two lines with different slopes will intersect only one time (if they're parallel they have the same slope)
100% = 25 so 25 + 15%
15% = .25 (25 divided by 100= .25) x 15 = 3.75
25 + 3.75 = 28.75 so C
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>
