I have decided to assume that there are several errors in this question. As the five possible answers are very similar it seems more likely that these lie in the start expression.
x^{5/6) leads to a cube root of 2 whereas we are hoping for a square root of 2. It is possible to show that no rational multiple of the first can give the second so that 6 must be in error. More likely a 4. This leads nicely to the (1+2root2) part of an answer.
56 is indeed a problem. How can a numerator with an integer and a root 3 lead to just a root 3. So I have altered the minus sign to a times sign.
9/2 leads to an 81 in the answer. Could it be 9^(1/2) rather than 9 times 1/2 ?
And x^-2 at the denominator leads to an answer that is far too large. Given that this is an exercise in fractional powers perhaps it should be x^(1/2)
So my suggestion is
This does lead to one of the given answers. You can have a try or uncover my hidden working.
Bob
Aw, thank you Bob! You really are a genius!
]]>x^{5/6) leads to a cube root of 2 whereas we are hoping for a square root of 2. It is possible to show that no rational multiple of the first can give the second so that 6 must be in error. More likely a 4. This leads nicely to the (1+2root2) part of an answer.
56 is indeed a problem. How can a numerator with an integer and a root 3 lead to just a root 3. So I have altered the minus sign to a times sign.
9/2 leads to an 81 in the answer. Could it be 9^(1/2) rather than 9 times 1/2 ?
And x^-2 at the denominator leads to an answer that is far too large. Given that this is an exercise in fractional powers perhaps it should be x^(1/2)
So my suggestion is
This does lead to one of the given answers. You can have a try or uncover my hidden working.
Bob
]]>I tried a few things in a brief attempt to work out how you got that answer, but didn't think of the missing parentheses.
]]>I agree with what you said, but I tried Monox D. I-Fly's problem in my calculator, Excel and Mathematica and get approx -574.028.
My Mathematica formula is N[(7x-9/2Surd[y^5, 6])/((x^(5/6)-6y^(-1/3))x^-2)], and my calculator and Excel methods follow that line.
I can't think what I might have done wrong...
]]>I too got stuck with this. So I tried evaluating the expression and the five possible answers and could find none that worked.
x^(5/6) seems to be a sticking point for me as that leads to a cube root of 2 not a square root. The answer must have a root of 3 in it.
If we're looking for a minimum typo to make this 'do-able' then losing the 7 would be a start … but that power 5/6 will have to change too … maybe 5/4 ???
I'll try exploring alternatives.
Bob
]]>I got stuck at
and don't know how to continue to reach one of the options. By the way, don't you think that 7 is suspicious?]]>