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# exponential function #2

evaluate the exponential function at the specified value of x

f(x)=4x,  x= -4

### 2 Answers by Expert Tutors

Jose S. | Friendly Mathematics, Philosophy, and Computer Science tutorFriendly Mathematics, Philosophy, and Co...
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Hey Carlos
You need to think about the rules for exponents. Is there any that tells you how to deal with negative exponents?

Here is a way to think about it.  For positive exponents you could write x^n = x*x^(n-1), as long as n is greater than 0.  This can be rewritten as: x^(n-1) = (x^n)/x, as long as x is not 0.  Now suppose n is 0, and the rule gives us: x^(-1) = x^(0)/x.  Since x^0 is 1, this means x^(-1) = 1/x.  If we assume this holds as long as n is an integer(positive or negative) and x is not 0, then we have that x^(-2) = x^(-1)/x = ([x^0]/x)/x =(1/x)/x = 1/x^2, and in general x^(-n) = 1/(x^n).  Then in your case, 4^(-4) = 1/(4^4).

From here just multiply to find: 1/(4*4*4*4)=?

Hope this is helpful,
Jose
Philip P. | Effective and Affordable Math TutorEffective and Affordable Math Tutor
5.0 5.0 (430 lesson ratings) (430)
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f(x) = 4x

f(x=4) = 44 = 4*4*4*4 = ??