Respuesta :
Solution: (-Infinite, -8/3] U (4, Infinite)
Using that a fraction is greater than or equal to zero when the numerator and denominator have the same sign:
a/b>=0. Then we have two cases:
Case 1) If the numerator is positive, the denominator must be positive too (at the same time):
if a>=0 ∩ b>0
Or (U)
Case 2) If the numerator is negative, the denominator must be negative too (at the same time):
if a<=0 ∩ b<0
In this case a=3x+8 and b=x-4, then:
Case 1):
if 3x+8>=0 ∩ x-4>0
Solving for x:
3x+8-8>=0-8 ∩ x-4+4>0+4
3x>=-8 ∩ x>4
3x/3>=-8/3 ∩ x>4
x>=-8/3 ∩ x>4
Solution Case 1: x>4 = (4, Infinite)
Case 2):
if 3x+8<=0 ∩ x-4<0
Solving for x:
3x+8-8<=0-8 ∩ x-4+4<0+4
3x<=-8 ∩ x<4
3x/3<=-8/3 ∩ x<4
x<=-8/3 ∩ x<4
Solution Case 2: x<=-8/3 = (-Infinite, -8/3]
Solution= Solution Case 1 U Solution Case 2
Solution = (4, Infinite) U (-Infinite, -8/3]
Solution: (-Infinite, -8/3] U (4, Infinite)
Using that a fraction is greater than or equal to zero when the numerator and denominator have the same sign:
a/b>=0. Then we have two cases:
Case 1) If the numerator is positive, the denominator must be positive too (at the same time):
if a>=0 ∩ b>0
Or (U)
Case 2) If the numerator is negative, the denominator must be negative too (at the same time):
if a<=0 ∩ b<0
In this case a=3x+8 and b=x-4, then:
Case 1):
if 3x+8>=0 ∩ x-4>0
Solving for x:
3x+8-8>=0-8 ∩ x-4+4>0+4
3x>=-8 ∩ x>4
3x/3>=-8/3 ∩ x>4
x>=-8/3 ∩ x>4
Solution Case 1: x>4 = (4, Infinite)
Case 2):
if 3x+8<=0 ∩ x-4<0
Solving for x:
3x+8-8<=0-8 ∩ x-4+4<0+4
3x<=-8 ∩ x<4
3x/3<=-8/3 ∩ x<4
x<=-8/3 ∩ x<4
Solution Case 2: x<=-8/3 = (-Infinite, -8/3]
Solution= Solution Case 1 U Solution Case 2
Solution = (4, Infinite) U (-Infinite, -8/3]
Solution: (-Infinite, -8/3] U (4, Infinite)
Answer:
The inequality is given to be :
[tex]\frac{3x+8}{x-4}\geq 0[/tex]
The inequality will be greater than or equal to 0 if and only if both the numerator and denominator of the left hand side will have same sign either both positive or both negative.
CASE 1 : Both positive
3x + 8 ≥ 0
⇒ 3x ≥ -8
[tex]x\geq \frac{-8}{3}[/tex]
Also, x - 4 ≥ 0
⇒ x ≥ 4
Now, Taking common points of both the values of x
⇒ x ∈ [4, ∞)
CASE 2 : Both are negative
3x + 8 ≤ 0
⇒ 3x ≤ -8
[tex]x\leq \frac{-8}{3}[/tex]
Also, x - 4 ≤ 0
⇒ x ≤ 4
So, Taking common points of both the values of x we have,
[tex]x=(-\infty,-\frac{8}{3}][/tex]
So, The solution of the equation will be the union of both the two solutions
So, Solution is given by :
[tex]x=(-\infty,-\frac{8}{3}]\:U\:[4,\infty)[/tex]
