document.write( "Question 389690: Without graphing, find the domain of the following functions:\r
\n" ); document.write( "\n" ); document.write( "a)\"f%28x%29+=+sqrt%28%28x+-+3%29%2F%282x%5E2+-+8%29%29\", and\r
\n" ); document.write( "\n" ); document.write( "b)\"f%28x%29+=+root%283%2C%28x+%2B+5%29%2F%28x%5E2+-+9%29%29\".
\n" ); document.write( "

Algebra.Com's Answer #276327 by robertb(5830)\"\" \"About 
You can put this solution on YOUR website!
a) Since there is a square root symbol, we have to ensure that \"%28x+-+3%29%2F%282x%5E2+-+8%29%3E=0\". To find the critical numbers, determine all x values that make either the top or the bottom equal to 0. By inspection they are -2, 2, and 3. These critical numbers partition the real number line into 4 parts. Choosing the test numbers -3, 0, 2.5, and 4, and checking for the signs:
\n" ); document.write( "For (\"-infinity\", -2), \"%28x+-+3%29%2F%282x%5E2+-+8%29+%3C+0\".
\n" ); document.write( "For (-2, 2), \"%28x+-+3%29%2F%282x%5E2+-+8%29%3E0\".
\n" ); document.write( "For (2,3), \"%28x+-+3%29%2F%282x%5E2+-+8%29%3C+0\".
\n" ); document.write( "For (3, \"infinity\"), \"%28x+-+3%29%2F%282x%5E2+-+8%29%3E+0\".
\n" ); document.write( "Of the critical numbers, only 3 can be accepted, and not 2 and -2. Therefore the domain is (-2, 2)U [3, \"infinity\").\r
\n" ); document.write( "
\n" ); document.write( "\n" ); document.write( "b) The radical symbol is a cube-root symbol, and every real number has a cube root (whether positive or negative). Then the only thing we have to ensure is that the denominator won't be 0. The x-values that make the denominator 0 are -3 and 3. Hence the domain is the set of all real numbers except -3 and 3, or R\{-3, 3}.
\n" ); document.write( "
\n" );