The function f(x)= -a^x +4 will never cross the x-axis. True or false??

Question

anonymous · Answer

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anonymous · Answer

I think its true

anonymous · Answer

um i agree with @NaomiBell1997

solomonzelman · Answer

I think it is true, also, it will approach it closely, but never cross

anonymous · Answer

can someone help me with my question

solomonzelman · Answer

I think I just did.

jdoe0001 · Answer

ali1029     do you know how $\bf y= x^2$ looks like?

ranga · Answer

If a > 1, the function can cross the x axis. 
y = -a^x +4 
To find where it crosses or touches the x axis, set y = 0 and solve for x 
0 = -a^x + 4 
add a^x to both sides 
a^x = 4 
take log on both sides
xlog(a) = log(4) 
x = log(4) / log(a) is the point where it will cut/touch the x axis for a > 1

anonymous · Answer

if a was positive, would the answer be false?