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- Thread starter Sombra
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First of all,write your inequation under the form

[tex] x^{2}+3x-10<0 [/tex]

Plot the parabola and see for which "x",the values of "y" (of the function whose graph is the parabola) are less than 0.

For the second part,please be more specific.Give an example,maybe...

Daniel.

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Thanks. For the second part, something like l 3x-4 l >5

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Okay,explicitate the modulus...According to its definition,of course...

Daniel.

Daniel.

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HallsofIvy

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A general technique for solving inequalities is to solve the equation first (just what you did) then check one point in each interval.

For example, to solve x

x

It's easy to calculate that (-6)

It's easy to calculate that 0

It's easy to calculate that 3

Likewise to solve |3x-4|> 5, first solve |3x- 4|= 5. Since absolute value "loses" the sign, either 3x-4= 5 or 3x-4= -5. In the first case, 3x= 9 so x= 3. In the second,

3x= -1 so x= -1/3.

The two points, x= -1/3 and x= 3 divide the number line into 3 intervals: x< -1/3,

-1/3< x< 3, and x> 3.

x= -1 is in x< -1/3. |3(-1)- 4|= |-7|= 7> 5. |3x-4|> 5 for all x< -1/3.

x= 0 is in -1/3< x< 3. |3(0)-4|= |-4|= 4< 5. |3x-4|< 5 for all x in -1/3< x< 3.

x= 4 is in x> 3. |3(4)-4|= |8|= 8> 5. |3x- 4|> 5 for all x> 3.

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What's the "catch",Halls??

Daniel.

P.S.Did i say somethin' stupid,again??? :yuck:

Daniel.

P.S.Did i say somethin' stupid,again??? :yuck:

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in this case, since both since are positiveSombra said:Thanks. For the second part, something like l 3x-4 l >5

you may squares both side so that the abs sign will no longer exist

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Mathematics is better comprehendable when put in the simpest terms...

Daniel.

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HallsofIvy

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I would think that most basic algebra students would not recognize the word "modulus" as meaning absolute value.

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Daniel.

P.S.I'm not used to spelling English words for math names...

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