Other Squaring / Square Roots - ACT Math

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Question

If (x - 3)2 = 64, what is a possible value of x?

Answer

In order to solve for x, we must first take the square root of both sides.

(x - 3)2 = 64

(x - 3) = +/- 8

The square root of 64 is either 8 or -8. We then solve the equation with both possible values of the square root of 64.

x - 3 = 8 (Add 3 to both sides.)

x = 11

x - 3 = -8 (Add 3 to both sides.)

x = -5

x = 11 or -5. -5 is the only possible value of x that is an answer choice.

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Question

When you square the following numbers, which one results in an irrational number?

Answer

A rational number is any number than can be expressed as a fraction or a quotient of two integers. The square of π is still an irrational number. (√(2))2 = 2, (1/3)2 = 1/9, (7/17)2 = 49/289, (1/2)2 = 1/4, all can be writen in fractional form, and are thus, rational numbers.

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Question

How much larger is the sum of the squares of –2, –3, and 4 than the sum of these integers?

Answer

The square of –2 is 4, of –3 is 9, and of 4 is 16.

The sum of these squares is 29.

The sum of (–2) + (–3) + (4) is –1.

29 – (–1) = 30

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Question

Solve: 3³

Answer

When using a cube root. 3³ becomes 3 * 3 * 3.

3 * 3 = 9

9 * 3 = 27

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Question

\dpi{100} \small \sqrt{15} is between what two integers?

Answer

\dpi{100} \small 3\times 3=9

\dpi{100} \small 4\times 4=16

falls between and

Therefore, \dpi{100} \small \sqrt{15} is between and

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Question

Simplify the following:

Answer

is the same as multiplied by . Thus, the answer is .

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Question

The last two digits in the square of a number have a product of . Which of the following could NOT be the last digit of ?

Answer

If the last two digits of the squared number multiply to , then the digits must be factors of . The last digit of any square of a number ending in will be , which is not a factor of . Thus, the number cannot end in .

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