So for a take-home review for my Algebra 2 class, there are two problems I just don't get. One is an equation where I need to solve for x and y.
4-3xi=7y+5i
with "i" being an imaginary number; the square root of -1.
The other is a system of equations I need to solve for x:
y=log(x)+5
y=log(x+5)
They're similar, but in one of them the 5 is outside the argument, and I just don't understand it, at all.
(Btw, my teacher said we had unlimited resources for the assignment so it's okay if I ask, I'm not cheating, haha.)
Thanks so much, if anyone can figure these out!
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Answers & Comments
Verified answer
for the first part, you have to make the assumption that x and y are real numbers otherwise there is no unique solution. That is, if they are not both real valued, then chose any y and let
x = (1 /3) * ( ( 7 y - 4) i - 5)
If they are both real valued then, since the real parts must be equal and the imaginary parts must be equal,
4 = 7 y
and
-3 x = 5
or
y = 4 / 7
x = - 5 / 3
For the second part, if you remember the part about the sum and difference of log functions, i.e.
log (x * y) = log(x) + log (y)
and
log (x / y) = log(x) - log(y)
it makes the problem easier. I will assume log is log base 10 so that log(10^5) = 5 and the first of the equations becomes
y = log(x) + log(10^5) = log(10^5 * x)
Thus
x + 5 = 10^5 x
or
x = 5 / (10^5 - 1) ~ .0000500005
so that
y ~ 0.69897435
Another way which doesn't depend on remembering the sum and difference log rules is to rewrite the equations by raising quantities to a poser of 10 and remembering that
10^(log(a)) = a
Write the first equation as
y - 5 = log(x)
and raise both sides to that power of ten:
10^(y-5) = 10^y / 10^5 = x
or 10^y = 10^5 x
Now the other equation to a power of ten gives
10^y = x + 5
which leads to the same equation for x as above.
4-3x(i) = 7y + 5(i)
7y = -3x(i) - 5(i) + 4
49Y = -9x'2 - 21
Y = -9/49x'2- 3/7
Now do a quadratic to solve for x. Im too tired to haha
Idk the other