SOLUTION: Why is it useful to rewrite a formula in terms of another variable?

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Question 655838: Why is it useful to rewrite a formula in terms of another variable?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Say you had +x%5E4+%2B+2x%5E2+-+8+=+0+
You could say +z=+x%5E2+
Then rewrite the equation:
+z%5E2+%2B+2z+-+8+=+0+
+%28+z+-+2+%29%2A%28+z+%2B+4+%29+=+0+
+z+=+2+
+z+=+-4+
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Now find +z+ in terms of +x+
+x%5E2+=+2+
+x+=+sqrt%282%29+
+x+=+-sqrt%282%29+
and
+x%5E2+=+-4+
+x+=+2i+
+x+=+-2i+