Q&A for How to Solve a Simple Linear Equation

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How do I answer (1 - 0.9)(1 - 0.2)?

Donagan

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That's (0.1)(0.8) = 0.08.

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How do you solve a question like, x-5=7?

Community Answer

In this example, move the 5 to the other side and change your action symbol, like this: x=7+5. Now, you can solve for x. To be sure you've done it correctly, put in your value for x in the original equation and solve.

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Question

How do I solve it if there are two variables?

Donagan

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You need two separate equations in those two variables.

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How do I solve -2 + (x-1)(x+2) = x(x-3) + 4(x-1)?

Donagan

Top Answerer

That equation has no solution, because it can be simplified to 4 = 4. That means the equation is true for all values of x, making it a "trivial" (useless) equation.

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How would I solve x + 7?

Donagan

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Because that's not an equation, it can't be solved.

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How do I solve (2x + 1)(x - 2) - x(2x - 1) = 0?

Donagan

Top Answerer

First perform the multiplication: (2x + 1)(x - 2) = 2x² - 4x + x - 2 = 2x² - 3x - 2 and (-x)(2x - 1) = -2x² + x. Then combine the two products and set the sum equal to zero: (2x² - 3x - 2) + (-2x² + x) = -2x - 2 = 0. Then -2x = 2, and x = -1.

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How would I solve 3x + 2 = 10 - 4(x - 1)?

Donagan

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3x + 2 = 10 - 4x + 4 = 14 - 4x. Add 4x to both sides: 7x + 2 = 14. Subtract 2 from both sides: 7x = 12. x = 12/7.

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How do I solve 5 to the power of 3 - 4 to the power of 2?

Donagan

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5³ - 4² = 125 - 16 = 109.

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How do you solve this equation: 5x + 7y = 18?

Community Answer

When you have one equation expressed in terms of two variables, all you can do is solve for one variable in terms of the other. In this case we can solve for x in terms of y, or y in terms of x. Let's do the former: first subtract 7y from both sides of the equation: 5x = 18 - 7y. Then divide both sides by 5: x = (18 - 7y) / 5. (In order to find numerical values for x and y, we would need a second independent equation also expressed in terms of x and y.)

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How do I know whether to add, subtract, multiply or divide?

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Use whatever operation is needed to isolate the variable, so that you can find the value of the variable. Examples: if x + 6 = 18, you would need to subtract 6 from both sides to isolate the x. If x - 6 = 4, you would need to add 6 to both sides to isolate the x. If 3x = 9, you would need to divide both sides by 3 to isolate the x. If x / 5 = 8, you would need to multiply both sides by 5 to isolate the x. (To isolate a variable means to have it alone on one side of the equation.)

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11y - 7 = 2y + 2a. How do you solve this?

Community Answer

With two variables in one equation, the most you can do is solve for one variable in terms of the other. In this case, if you subtract 2y from both sides and add 7 to both sides, and then divide both sides by 9, you find that y = (2a + 7) / 9. Instead, if you subtract 2y from both sides and then divide both sides by 2, you find that a = (9y - 7) / 2.

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How do I solve -29 = 5(2a-1) + 2a?

Community Answer

-29 = 5(2a - 1) + 2a = 10a - 5 +2a = 12a - 5. Add 5 to both sides: -24 = 12a. Divide both sides by 12: a = -2.

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How do I verify -10x = 33? (I know the solution is -33/10, but don't know how to verify.)

Community Answer

You verify by plugging the x-value back into the original equation to see if the equation is valid using that x-value. In this case, (-10)(-33/10) does equal +33, and the solution is verified.

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How would I solve y = 50 - 2x?

Community Answer

All you can do is solve for one of the variables in terms of the other. You're given the value of y. To find the value of x, subtract 50 from both sides of the equation, and then divide both sides by -2. We find that x = (y - 50) / -2 = (50 - y) / 2.

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Is there a specific order in which to do the properties? Do I follow PEMDAS?

I_l1ke_gam3s

Community Answer

It is best to follow PEMDAS (known in some places as BODMAS or BEDMAS) when you have multiple operations, as it is easy to make a big mistake if you don't.

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What about y=7? What is the m and b in that equation?

Community Answer

That equation could be written as y = 0x + 7. In other words, m = 0, and b = 7. With a slope of 0, the graph of that equation is a straight, horizontal line crossing the y-axis at +7. That means that for any value of x, y will equal 7.

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