## anonymous 5 years ago find any real number for which the rational expression is undefined a-5/7

1. anonymous

is it (a-5)/7 or a-(5/7)???

2. anonymous

(a-5)/7

3. anonymous

it's defined for all values of a.. if you were asking about $7 \over a-5$ then it would be undefined at $a-5=0 \implies a=5$

4. anonymous

so then answer would be 0 or 5?

5. anonymous

the answer to your question would be "phi" (since there is no a where (a-5)/7 the expression undefined)

6. anonymous

I meant by phi the empty set.. looks I am complicating things!! :) you just need to know that the expression you gave is defined for all values of a. that's it

7. anonymous

ok thanks