To the power 4

[sakurle]

If x^4 + y^4 = 100 greatest value of x is between

A. 0 and 3
B. 3 and 6
C. 6 and 9
D. 9 and 12
E. 12 and 15

The answer has to be either A or B, but which would you choose.

[bharathh]

A

For any of the other options x^4 would be > 100 and y^4 cannot be negative.

[tom4lax]

Actually i think the answer is B. 3^2=9, so x can be greater than 3, falling between 3 and 6.

[bharathh]

Hmm.. you could be right.

Dammit I was on a roll today

2 questions wrong then

Ok .. you def are correct

[sakurle]

Yes the right answer is B between 3 to 6, but I am not sure how. Because if you take 4 4^4 is above 100.

However if you take x as 3.1, then x^4 = 92.351 which is still less than 100, and then y can taka a value such that y^4 added to x^4 can be 100. May be that is why the answer is B.

[tohellandback]

If x^4 + y^4 = 100 greatest value of x is between

A. 0 and 3
B. 3 and 6
C. 6 and 9
D. 9 and 12
E. 12 and 15

The answer has to be either A or B, but which would you choose.

IMO B
to maximize x^4 minimize y^4
y=0
for x=3, x^4=81
for x=4, x^4= 256
so x must be greater than 3 but less than 4
only B satisfies this

[Nermal]

I agree with you guys, but I would first take the squareroot of everything.

x^2+y^2=10

if y=0, then x^2=10, x=sqrt10=3,16...

[sakurle]

I am not sure I understand your logic. I don't think sqrt(x^4 + y^4) is same as x^2+y^2.

[Nermal]

Maybe because there was no logic.
Sorry, this was a very stupid mistake!