Câu 1. Cho mệnh d dot hat e :^ *** forall x in mathbb R ,x^ 2 +3x+5>0" Mệnh đề phủ định của mệnh đề trên là A. forall x in mathbb R ,x^ 2 +3x+5<=0 . C. forall x in mathbb R .x^ 2 +3x+5<0 . B. exists x in mathbb R ,x^ 2 +3x+5<=0 . D. exists x in mathbb R ,x^ 2 +3x+5>0 .

since your problem is x^4 = 81, what you have to undeo is the "to the fourth power" part.

the inverse (opposite operation) of "to the fourth power" is "to the fourth root".

  (x^4) ^ ¼   = 81 ^ ¼  

  81 = 3^4     so (3 ^ 4) ^ ¼   =   3 ^ 1   = 3

by hand: (3 ^ 4) ^ ¼   =   3 ^ (4 x ¼) = 3 ^ 1   = 3   (when you take a power to a power, multiply the exponents.)

or, do it by calculator. one way of finding the fourth root is to use ^ (1/4)

step-by-step explanation:

6 hours 48 min

step-by-step explanation:

68÷5=13.6

13.6×30=408min=6 hours 48 min.

hope to and hope that my answer is brainliest.(follow me )

the answer is 8.64

step-by-step explanation: