How to find the solution to an inequality with subtraction - ACT Math

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Question

Given that x = 2 and y = 4, how much less is the value of 2_x_2 – 2_y_ than the value of 2_y_2 – 2_x_ ?

Answer

First, we solve each expression by plugging in the given values for x and y:

2(22) – 2(4) = 8 – 8 = 0

2(42) – 2(2) = 32 – 4 = 28

Then we find the difference between the first and second expressions’ values:

28 – 0 = 28

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Question

The cost, in cents, of manufacturing \dpi{100} \small x pencils is \dpi{100} \small 1200+20x, where 1200 is the number of cents required to run the factory regardless of the number of pencils made, and 20 represents the per-unit cost, in cents, of making each pencil. The pencils sell for 50 cents each. What number of pencils would need to be sold so that the revenue received is at least equal to the manufacturing cost?

Answer

If each pencil sells at 50 cents, \dpi{100} \small x pencils will sell at \dpi{100} \small 50x. The smallest value of \dpi{100} \small x such that

\dpi{100} \small 50x\geq 1200+20x

\dpi{100} \small x\geq 40

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Question

Solve

Answer

Absolute value problems are broken into two inequalities: and . Each inequality is solved separately to get and . Graphing each inequality shows that the correct answer is .

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Question

Which of the following inequalities defines the solution set to ?

Answer

First, move the s to one side.

Subtract by 1

Divide both sides by 7.

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Question

Solve the following inequality:

Answer

To solve an inequality with subtraction, simply solve it is as an equation.

The goal is to isolate the variable on one side with all other constants on the other side. Perform the opposite operation to manipulate the inequality.

In this case add two to each side.

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Question

Solve the following inequality:

Answer

To solve, simply treat it as an equation.

This means you want to isolate the variable on one side and move all other constants to the other side through opposite operation manipulation.

Remember, you only flip the inequality sign if you multiply or divide by a negative number.

Thus,

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