When y=125 and x=-3, what is the value of #root3y-3x^4#?

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Answer 1 · 2017-01-06T03:02:49

Let #x=-3#
Let #y=125#
#root3(y)-3x^4=#

#-238#

#root3(y) -3x^4#

Let's break this down starting with #y#.

#root3(125) = 5#
because #n*n*n = n^3# and #root3(n^3)=n#.

#5^3=125# [how convenient :)]

#root3(125)=5#

Now #x#.

#3(-3)^4#

Recall PEMDAS: Parentheses first, then exponents. You have to take account for that negative.

#-3*-3*-3*-3 = 81#

#81*3=243#

Finally:

#5 - 243 = -238#