How to factor a variable - ACT Math

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Question

Simplify:

Answer

factors to

One cancels from the bottom, leaving

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Question

Two consecutive positive multiples of five have a product of 300. What is their sum?

Answer

Define the variables as x = 1st number and x + 5 = 2nd number, so the product is given as x(x + 5) = 300, which becomes x2 + 5x – 300 = 0.

Factoring results in (x + 20)(x – 15) = 0, so the positive answer is 15, making the second number 20.

The sum of the two numbers is 35.

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Question

Factor 12_x_3_y_4 + 156_x_2_y_3

Answer

The common factors are 12, x2, and y3.

So 12_x_2_y_3(xy + 13)

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Question

Factor:

Answer

In the form of you must find two numbers which add to give you and multiply to give you and then put them in the form of ( + number) ( + number)

Therefore is the answer.

To check, multiply the two expressions out and it should equal

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Question

Solve for all solutions of \dpi{100} \small x:

\dpi{100} \small 2x^{2}-10x=x^{2}-24

Answer

First move all of the variables to the left side of the equation. Combine similar terms, and set the equation equal to zero. Then factor the equation to get \dpi{100} \small (x-4)(x-6)=0

Thus the solutions of \dpi{100} \small x are 4 and 6.

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Question

Factor the following expression:

Answer

To factor an expression we look for the greatest common factor.

Remember that

Thus:

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Question

Factor the following expression:

Answer

To factor, you are looking for two factors of 40 that add to equal 13.

Factors of 40 include: (1, 40), (2, 20), (4, 10), (5, 8). Of these factors which two will add up to 13?

Also, since the first sign (-) and the second sign is (+) this tells us both binomials will be negative. This is because two negatives multiplied together will result in the positive third term, while two negatives added together will result in a larger negative number.

Thus,

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