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<p>The graph above shows the function g, where g(x) = k(x+3)(x-3), for some constant k,</p>
<p>If g(a-1.2) = 0 and a > 0, what is the value of a ?</p>
<p>The answer is 4.2</p>
<p>I Solved this question but it took me between 4-5 minutes So, I wanted to know if there's a faster way.</p>
<p>Think of it this way:</p>
<p>g(a-1.2)=0 </p>
<p>This is pretty much asking at what point does g=0</p>
<p>Since g(x) (or g(a-1.2)) is considered the Y coordinate, you know in this case that Y=0</p>
<p>Based on the graph, at what point on the graph does Y=0? You can see that when X=3, Y=0</p>
<p>Now that you know the X coordinate, you know that a-1.2=3 since the a-1.2 acts as the X in g(x). Through basic algebra, you can then find that a=4.2</p>
<p>I hope that makes sense. I’m not sure if you used that method to solve this yourself, but if you keep practicing, you should be able to easily solve this in much less than a minute. Quite honestly, just think of the g(x) or g(a-1.2)=0 as y=0, and just find the corresponding X coordinate by looking on the graph first. Once you find the X coordinate, plug it into the equation and you’ll find the answer.</p>
<p>Hope this helped.</p>
<p>Thank you this really helped, it actually takes less than 30 seconds.</p>
<p>This is such a brilliant idea!
Why have I never thought of that?</p>
