4^(x+2)+64=0........20point!!!

2010-01-28 1:17 am
4^(x+2)+64=0
x=??????????
who can help me???
更新1:

gmklaw1966...you are wrong....... 4^-3+4^3 is not equals to 0 4^-3+4^3 = 1/64 + 64 does not equals to 0 THX Who can help me!!!!!!!

回答 (2)

2010-01-28 2:43 am
✔ 最佳答案
I think your question have some typing error.
4^(x+2)+64=0 have no solution for x , it is because
4^k is always > 0 for any real number k , so RHS = 4^k + 64 is always > 0
= LHS.
You can see the problem by taking log :
4^(x+2)+64=0
4^(x+2) = - 64
(x+2)log4 = log (-64)
But log (-64) is not a real number!!
negative number can't be taken log !!

If the question is : 4^(x+2) - 64 =0 , then
4^(x+2) - 64 =0
4^(x+2) = 64
4^(x+2) = 4^3
x+2 = 3
x = 1
2010-01-28 1:40 am
2^2(x+2)+2^6=0

2(x+2)+6=0 [Remove Base 2]

2x+4+6=0

2x+10=0

x=-5

Check [Substitue x=-5 in equation]:

4^(-5+2)+64=0

4^-3+4^3=0

0=0 ......OK
參考: Index Rules


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