i end up with x^2-x-15=0, is this correct?
2007-05-22 01:10:50 · 9 answers · asked by Shukie L 1 in Science & Mathematics ➔ Mathematics
log(x+2)+log(x-3) = log9
log[(x+2)(x-3)]=log9?
(x+2)(x-3) = 9
x²-x-6=9
x²-x-15=0
Well I get the same answer.
2007-05-22 01:16:15 · answer #1 · answered by Astral Walker 7 · 0⤊ 0⤋
First x+2>0 so x>-2 and x-3>0 so x>3 (this is the condition
so
(x+2)(x-3)=9 and x^2-x-15 = 0
x=((1+-sqrt(61))/2 = (1+-7.81)/3 x=4.405 and
x= -3.405 which is NOT a solution
Negative numbers don´t have log
2007-05-22 07:27:03 · answer #2 · answered by santmann2002 7 · 0⤊ 0⤋
(a) use the rule of thumb: log (ab) = log (a) + log (b) hence, log9 (3x) = log9 (3) + log9(x) = a million/2 + u (b) use the actuality that if u = log9 (x) then x = 9^u logx (80 one) =log 9^u (80 one) =log 9^u (9^2) hence, 9^ui = 9^2 and resolve for i ui = 2 i = 2/u
2016-11-26 00:36:42 · answer #3 · answered by abila 4 · 0⤊ 0⤋
(x + 2).(x - 3) = 9
x² - x - 6 = 9
x² - x - 15 = 0 (so far ,so good!)
x = [1 ± √(1 + 60)] / 2
x = [1 ± √(61)] / 2
Which is in acceptable form as an answer.
An approximate answer would be obtained by evaluating √61.
2007-05-22 08:28:27 · answer #4 · answered by Como 7 · 0⤊ 0⤋
The question reduces to :
(X + 2) ( X - 3 ) = 9.
X ^ 2 - X -15 = 0
So u are correct.
On solving we get,,
X = 4.40 or X = -3.405
2007-05-22 07:18:09 · answer #5 · answered by karan 1 · 0⤊ 0⤋
yes ,
log(x+2)(x-3)=log9
x^2 -x -6 -9=0
2007-05-22 01:22:49 · answer #6 · answered by nasser a 2 · 0⤊ 0⤋
It is right.But you must know the "a\b\c"in Log a(x+2)+Log b(x-3)= Logc(9).
The "a\b\c"must be the same one.
a=b=c.
2007-05-22 01:39:14 · answer #7 · answered by Anonymous · 0⤊ 0⤋
It looks correct to me.
2007-05-22 01:15:21 · answer #8 · answered by Anonymous · 0⤊ 0⤋
yep
2007-05-22 01:14:52 · answer #9 · answered by mikedotcom 5 · 0⤊ 0⤋