Answer:
76
Step-by-step explanation:
The last two digits of powers of 36 repeat in a pattern of length 5:
36^1 mod 100 = 36
36^2 mod 100 = 96
36^3 mod 100 = 56
36^4 mod 100 = 16
36^5 mod 100 = 76
36^6 mod 100 = 36
The last two digits of the power 2015 are the same as those of the 5th power: 76.
First join the log4 on the left:
log4( x*(x-3) = log4(-7x+21)
Then x = -7, works: -7*(-10)=70 = -7*(-7)+21
x=-3, 18 = 42, does not work
x=3 0=0 works,
However, when one puts x = -7 in the *original* exression, log4(-7) or log4(-10) do not exist (you know why?). So x= -7 is extraneous.
Now x=3 gives log4(0) on the left and right, which does not exist.
So, C is the answer, both are extraneous. Seem to work but indeed don't work in the *original* equation
To find invers
1. solve for y
2. replace y with xinverse
so
x=4-4y+y^2
reorder right side
x=y^2-4y+4
factor right side
x=(y-2)^2
squaer root both sides
+/-√x=y-2
add 2 to both sides
2+/-√x=y
switch x and y
2+/-√y=xinverse
xinverse=2+√y or 2-√y
subtract 4 from both sides
