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maths inequalities help please!?
x/(x+3) is greater than 1/(x-2)
any help is really appreciated, got my exam tomorrow
3 Answers
- Old TeacherLv 710 years agoFavorite Answer
This is different from an equation. You cannot cross-multiply.
Pull everything to one side and get a common denominator.
X/(x+3)-1/(x-2) >0. The lcd is (x+3)(x-2)
[X(x-2)-1(x+3)]/(x+3)(x-2)>0
(x^2-2x-x-3)= x^2-3x-3 is the numerator, but does not factor
So (x^2-3x-3)/(x+3)(x-2)>0
you now have to find the zeroes of all the factors
X= -3, or 2 are zeroes of the denominator. Unfortunately you have to use the quadratic formula for the numerator.
X= (3+/-sqr(21))/2=3.9or-.8
Now put all these numbers on a number line
.......-3.......-.8........2..........3.9......
So check all five regions to see which ones work!
+...-3.....(-)......-8......(+).....2.....(-).....3.9....+.....
so the solution is ( -infinity,-3) and( -.8,2) and (3.9, infinity)
This is sooo much easier with a graphing calculator...just graph both sides and see where the first graph is above (>) the other.
Good luck!
Source(s): Math teacher - 10 years ago
x/(x+3) > 1/(x-2)
multiply both sides by (x + 3)(x - 2)
now the inequality reads
x^2 - 2x / (x + 3)(x - 2) > x + 3 / (x + 3)(x - 2)
multiply both sides by (x + 3)(x - 2)
now the inequality reads
x^2 - 2x > x + 3
x^2 - 3x - 3 > 0
now use the quadratic formula.
- ?Lv 45 years ago
There are two inequalities: 2w > eight AND 2w < 12 You can remedy it now. The first one says w > four. The moment one says w < 6. So the reply is "w > four AND w < 6". You can write this as "four < w < 6".