3x+8=2x+21 X=? (all working out needed)
2 answers:
You might be interested in
Answer:
see below
Step-by-step explanation:
Put -1 where x is in each expression and evaluate it.
__
You will find that the expression is zero when the numerator is zero. And you will find the numerator is zero when it has a factor that is equivalent to ...
(x +1)
Substituting x=-1 into this factor makes it be ...
(-1 +1) = 0
__
Evaluating the first expression, we have ...
This first expression is one you want to "check."
You can see that the reason the expression is zero is that x+1 has a sum of zero. You can look for that same sum in the other expressions. (The tricky one is the one with the factor (x -(-1)). You know, of course, that -(-1) = +1.)
