x^4 + y^4 =100
As y^4>=0 then maximum value of x^4 is 100
then x^2 = sqrt(100) = 10 ( why not -10?, as x^2 is always equal to or larger than 0)
Hence x = sqrt(10) (why not -sqrt(10)?, as -sqrt(10) < sqrt(10), and we are asked to pick the maximum x)
For all positive numbers larger than 1: a>b then a^2>b^2 and vice versa
Pick some value from the choices, such as 3
3^2 = 9, while x^2 = 10,as 10>9 then x>3 ( I mean the x that is positive here. There is another x that is negative - the -sqrt(10) "x" that we eliminate above)
6^2 = 36, as 36>10 then x<6
Pick B.
Last edited by
limestone on Mon Sep 27, 2010 8:28 pm, edited 1 time in total.
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