Need help solving/graphing some inequalities

As x goes from negative numbers to -2, x3+ 2x2- 3x- 6 decreases from a large negative value to 0: it is negative on x< -2. As x goes from -2 to -\sqrt{3}, x3+ 2x2- 3x- 6 decreases from 0 to a negative value: it is positive on -2< x< -\sqrt{3}. As x goes from -\sqrt{3} to \sqrt{3}, x3+ 2x2- 3x- 6 increases from a negative value through 0 to a positive value: it is negative on -\sqrt{3
  • #1
rought
34
0
Alright again I am having trouble with a few problems.

I am unsure on the first two problem's answers and I have no idea how to do the third one..Solve and graph the solution on a number line

0 < |x + 3| < 1

I get: -3 < X < -2 or -3 > X > -4

and it graphs like this (is this right?) [horrible picture sorry]

a47sds.png



Graph the solution set on a coordinate of axes
(I know how to graph it I am just unsure on the points)

1 ≤ |X - 4| ≤ 3

1 ≤ |Y - 4| ≤ 3

I ended up getting

5 ≤ Y ≤ 7 or 3 ≥ Y ≥ 1

and the same for X

5 ≤ X ≤ 7 or 3 ≥ X ≥ 1

Is that right? =/

Ok and this last one I have no idea how to solve :confused:

Solve: X^3 + 2x^2 > 3X + 6
 
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  • #2
Ok I think I have the first two figured out but I am still stuck on

Solve: X^3 + 2x^2 > 3X + 6
 
  • #3
The best way to solve any complicated inequality is to first solve the associated equation.

x3+ 2x2> 3x+ 6 is the same as x3+ 2x2- 3x- 6> 0 and the associated equationj is x3+ 2x2- 3x- 6= 0.

If there are any rational solutions to that they must divide 6 and so are 1, -1, 2, -2, 3, -3, 6, or -6. Trying each of those we see that (-2)3+ 2(-2)2- 3(-2)- 6= -8+ 8+ 6- 6= 0 so x= -2 is a root. Dividing by (x+ 2) we get x2- 3 as quotient and [itex]x= \pm\sqrt{3}[/itex] as the other 2 roots. The numbers, -2, [itex]-\sqrt{3}[/itex], and [itex]\sqrt{3}[/itex] separate all real numbers into four intervals: x< -2, [itex]-2< x< -\sqrt{3}[/itex], [itex]-\sqrt{3}<\sqrt{3}[/itex], and [itex]\sqrt{3}< x[/itex]. Since the polynomial x3+ 2x2- 3x- 6 is continuous it can change sign only at those points where it is 0. Check on point in each interval to determine whether the numbers in that interval make the value positive or negative.
 

Related to Need help solving/graphing some inequalities

1. What are inequalities?

Inequalities are mathematical expressions that use the symbols <, >, ≤, or ≥ to compare two quantities. They show the relationship between numbers or variables, indicating which is greater or smaller than the other.

2. How do I solve an inequality?

To solve an inequality, follow the same rules as solving an equation, with one exception: if you multiply or divide both sides by a negative number, the direction of the inequality sign must be reversed. The solution is the set of all values that make the inequality true.

3. What is the difference between an open and closed circle in graphing inequalities?

In graphing inequalities, an open circle is used to represent a strict inequality (< or >), while a closed circle is used for a less strict inequality (≤ or ≥). This indicates whether the endpoint is included in the solution or not.

4. How do I graph an inequality on a number line?

To graph an inequality on a number line, first determine the inequality symbol and the number that represents the endpoint. For a strict inequality, use an open circle on the number line at the endpoint. For a less strict inequality, use a closed circle. Then, shade the region on the number line that represents the solution set.

5. What are the key things to remember when solving and graphing inequalities?

When solving and graphing inequalities, there are a few key things to remember. First, always follow the rules of solving equations, with the exception of reversing the inequality sign if multiplying or dividing by a negative number. Second, pay attention to the type of inequality (strict or less strict) when graphing on a number line. Finally, always check your solution to make sure it is correct and accurate.

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