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
Answer: (m-21)(m+1)
Step-by-step explanation:
To factor this trinomial, find two numbers that multiply to -21 and add to -20:
(-21)(1)=-21
-21+1=-20
They are -21 and 1.
Add -21 and 1 to m to get both factors:
(m+(-21)) and (m+1)
(m-21) and (m+1)
Multiply them to get the answer:
(m-21)(m+1)
186cm
You add all the sides up, so 42+42+51+51 which equals 186cm
