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What value of [tex]$x$[/tex] is in the solution set of the inequality [tex]$-5x - 15 \ \textgreater \ 10 + 20x$[/tex]?

A. [tex][tex]$-2$[/tex][/tex]
B. [tex]$-1$[/tex]
C. [tex]0$[/tex]
D. [tex]1$[/tex]


Sagot :

To find the value of [tex]\( x \)[/tex] that solves the inequality [tex]\( -5x - 15 > 10 + 20x \)[/tex], we will follow these steps:

1. Move all terms involving [tex]\( x \)[/tex] to one side of the inequality and constants to the other:

[tex]\[ -5x - 15 - 20x > 10 \][/tex]

2. Combine like terms:

[tex]\[ -25x - 15 > 10 \][/tex]

3. Isolate [tex]\( x \)[/tex] by first moving the constant term to the other side:

[tex]\[ -25x > 10 + 15 \][/tex]

4. Simplify the right-hand side:

[tex]\[ -25x > 25 \][/tex]

5. Divide both sides of the inequality by -25, and remember to reverse the inequality sign because we are dividing by a negative number:

[tex]\[ x < \frac{25}{-25} \][/tex]

[tex]\[ x < -1 \][/tex]

Now, we need to check the given options:

1. [tex]\( x = -2 \)[/tex]:

[tex]\[ -5(-2) - 15 > 10 + 20(-2) \][/tex]

Simplifying,

[tex]\[ 10 - 15 > 10 - 40 \][/tex]

[tex]\[ -5 > -30 \][/tex]

This is true. So, [tex]\( x = -2 \)[/tex] is a solution.

2. [tex]\( x = -1 \)[/tex]:

[tex]\[ -5(-1) - 15 > 10 + 20(-1) \][/tex]

Simplifying,

[tex]\[ 5 - 15 > 10 - 20 \][/tex]

[tex]\[ -10 > -10 \][/tex]

This is false. So [tex]\( x = -1 \)[/tex] is not a solution.

3. [tex]\( x = 0 \)[/tex]:

[tex]\[ -5(0) - 15 > 10 + 20(0) \][/tex]

Simplifying,

[tex]\[ -15 > 10 \][/tex]

This is false. So [tex]\( x = 0 \)[/tex] is not a solution.

4. [tex]\( x = 1 \)[/tex]:

[tex]\[ -5(1) - 15 > 10 + 20(1) \][/tex]

Simplifying,

[tex]\[ -5 - 15 > 10 + 20 \][/tex]

[tex]\[ -20 > 30 \][/tex]

This is false. So [tex]\( x = 1 \)[/tex] is not a solution.

Thus, the value of [tex]\( x \)[/tex] which satisfies the given inequality is [tex]\( \boxed{-2} \)[/tex].