Given the inequality:
(x+2)(x+3)(x+5)>0To solve this inequality, we must first solve the corresponding equation:
(x+2)(x+3)(x+5)=0Solve:
Given the equation:
(x+2)(x+3)(x+5)=0Because the right side of the equation is zero, then the solution of the equation is exists if at least one of the multipliers in the left side of the equation equal to zero.
We get the equations
x+2=0x+3=0x+5=0solve the resulting equation:
1.
x+2=0Move free summands (without x)
from left part to right part, we given:
x=−2We get the answer: x1 = -2
2.
x+3=0Move free summands (without x)
from left part to right part, we given:
x=−3We get the answer: x2 = -3
3.
x+5=0Move free summands (without x)
from left part to right part, we given:
x=−5We get the answer: x3 = -5
x1=−2x2=−3x3=−5x1=−2x2=−3x3=−5This roots
x3=−5x2=−3x1=−2is the points with change the sign of the inequality expression.
First define with the sign to the leftmost point:
x0<x3For example, let's take the point
x0=x3−101=
−5+−101=
−1051substitute to the expression
(x+2)(x+3)(x+5)>0(−1051+2)(−1051+3)(−1051+5)>0-651
----- > 0
1000
Then
x<−5no execute
one of the solutions of our inequality is:
x>−5∧x<−3 _____ _____
/ \ /
-------ο-------ο-------ο-------
x3 x2 x1
Other solutions will get with the changeover to the next point
etc.
The answer:
x>−5∧x<−3x>−2