Question

Please answer this question faast....
If a^2+9/a^2=31, what will be the value of a-3/a

Answer 1

a² + 9  
--------   = 31
   a²
Using cross-multiplication method,
⇒ 31a² = a²+9
⇒ 31a² - a² = 9
⇒ 30a² = 9
⇒ a² = 9/30
⇒ a =  √9
          -----
          √30
⇒ a =    3
           -----
           √30.

Putting value of a in a-3/a,
         3/√30 - 3
⇒    ----------------
            3/√30
        √30 X √30 - 3
⇒     -------------------
              3 X 3
⇒  30 - 3/9
⇒  27/9
⇒  3

Hence, the answer is 3.
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