SAT Math : Algebra

Study concepts, example questions & explanations for SAT Math

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Example Questions

Example Question #2 : Squaring / Square Roots / Radicals

Simplify: \displaystyle (3n+5)^2

Possible Answers:

\displaystyle 9n^2+8n+10

\displaystyle 9n^2+8n+25

\displaystyle 9n^2-25

\displaystyle 9n^2+30n+25

\displaystyle 9n^2+25

Correct answer:

\displaystyle 9n^2+30n+25

Explanation:

If you don't already have the pattern memorized, use FOIL. It's best to write out the parentheses twice (as below) to avoid mistakes:

\displaystyle (3n+5)^2

\displaystyle (3n+5)(3n+5)

\displaystyle 9n^2+15n+15n+25

\displaystyle 9n^2+30n+25

Example Question #64 : Exponents

x2 = 36

Quantity A: x

Quantity B: 6

Possible Answers:

Quantity B is greater

Quantity A is greater

The two quantities are equal

The relationship cannot be determined from the information given

Correct answer:

The relationship cannot be determined from the information given

Explanation:

x2 = 36 -> it is important to remember that this leads to two answers. 

x = 6 or x = -6. 

  If x = 6: A = B.

  If x = -6: A < B.

Thus the relationship cannot be determined from the information given.

Example Question #1 : Squaring / Square Roots / Radicals

According to Heron's Formula, the area of a triangle with side lengths of a, b, and c is given by the following:

Hero

where s is one-half of the triangle's perimeter. 

 

What is the area of a triangle with side lengths of 6, 10, and 12 units?

Possible Answers:

48√77

12√5

4√14

14√2

8√14

Correct answer:

8√14

Explanation:

We can use Heron's formula to find the area of the triangle. We can let a = 6, b = 10, and c = 12.

In order to find s, we need to find one half of the perimeter. The perimeter is the sum of the lengths of the sides of the triangle.

Perimeter = a + b + c = 6 + 10 + 12 = 28

In order to find s, we must multiply the perimeter by one-half, which would give us (1/2)(28), or 14.

Now that we have a, b, c, and s, we can calculate the area using Heron's formula. 

Hero

Hero2

 

 

Example Question #2 : Squaring / Square Roots / Radicals

Simplify the radical expression.

\displaystyle \sqrt[3]{-64x^{6}y^{12}}

Possible Answers:

\displaystyle -2x^3y^4

\displaystyle 4ix^2y^4

\displaystyle -4x^{2}y^{4}

\displaystyle 2ix^3y^4

Correct answer:

\displaystyle -4x^{2}y^{4}

Explanation:

\displaystyle \sqrt[3]{-64x^{6}y^{12}}

Look for perfect cubes within each term. This will allow us to factor out of the radical.

\displaystyle \sqrt[3]{-64}*\sqrt[3]{x^6}*\sqrt[3]{y^{12}}

\displaystyle \sqrt[3]{-4*-4*-4}*\sqrt[3]{x^2*x^2*x^2}*\sqrt[3]{y^4*y^4*y^4}

Simplify.

\displaystyle -4x^{2}y^4

Example Question #3 : Squaring / Square Roots / Radicals

Simplify the expression.

\displaystyle \sqrt{5}(2\sqrt{3}+\sqrt{12})

Possible Answers:

\displaystyle 10\sqrt{15}

\displaystyle 4\sqrt{15}

\displaystyle 10\sqrt{3}

\displaystyle 3\sqrt{2}

\displaystyle 4\sqrt{30}

Correct answer:

\displaystyle 4\sqrt{15}

Explanation:

Use the distributive property for radicals. 

\displaystyle \sqrt{5}(2\sqrt{3}+\sqrt{12})

Multiply all terms by \displaystyle \sqrt{5}.

\displaystyle (\sqrt{5}*2\sqrt{3})+(\sqrt{5}*\sqrt{12})

Combine terms under radicals.

\displaystyle 2\sqrt{3*5}+\sqrt{12*5}

\displaystyle 2\sqrt{15}+\sqrt{60}

Look for perfect square factors under each radical. \displaystyle 60 has a perfect square of \displaystyle 4. The \displaystyle 4 can be factored out.

\displaystyle 2\sqrt{15}+\sqrt{4*15}

\displaystyle 2\sqrt{15}+2\sqrt{15}

Since both radicals are the same, we can add them.

\displaystyle 4\sqrt{15}

Example Question #2 : Squaring / Square Roots / Radicals

Which of the following expression is equal to

\displaystyle \sqrt{(45)(9)+(27)(36)}

 

Possible Answers:

\displaystyle 7\sqrt{17}

\displaystyle 7\sqrt{15}

\displaystyle 9\sqrt{19}

\displaystyle 9\sqrt{17}

\displaystyle 9\sqrt{15}

Correct answer:

\displaystyle 9\sqrt{17}

Explanation:

\displaystyle \sqrt{(45)(9)+(27)(36)}

When simplifying a square root, consider the factors of each of its component parts:

\displaystyle \sqrt{(3^2)\times5\times(3^{2})+(3^{3})(2^2)(3^2)}

Combine like terms:

\displaystyle \sqrt{5(3^4)+(2^2)(3^5)}

Remove the common factor, \displaystyle 3^4:

\displaystyle \sqrt{(3^4)\times(5+3\times(2^2))}

Pull the \displaystyle \sqrt{3^4} outside of the equation as \displaystyle 3^2:

\displaystyle (3^2)\sqrt{5+12}=9\sqrt{17}                       

Example Question #2321 : Act Math

Which of the following is equal to the following expression?

\displaystyle \sqrt{(16)(8)+(32)(20)}

Possible Answers:

\displaystyle 2^{4}\sqrt{5}

\displaystyle 2^{3}\sqrt{10}

\displaystyle 2^{7}\sqrt{5}

\displaystyle 2^4\sqrt{3}

\displaystyle 2^{3}\sqrt{6}

Correct answer:

\displaystyle 2^4\sqrt{3}

Explanation:

\displaystyle \sqrt{(16)(8)+(32)(20)}

First, break down the components of the square root:

\displaystyle \sqrt{(2^{4})(2^{3})+(2^{5})(2^{2})\times 5}

Combine like terms. Remember, when multiplying exponents, add them together:

\displaystyle \sqrt{(2^{7})+(2^{7})\times5}

Factor out the common factor of \displaystyle 2^7:

\displaystyle \sqrt{(2^{7})(1+5)}

\displaystyle \sqrt{(2^7)\times6}

Factor the \displaystyle 6:

\displaystyle \sqrt{(2^7)\times2\times3}

Combine the factored \displaystyle 2 with the \displaystyle 2^7:

\displaystyle \sqrt{(2^{8})\times3}

Now, you can pull \displaystyle \sqrt{2^8} out from underneath the square root sign as \displaystyle 2^4:

\displaystyle 2^4\sqrt{3}

Example Question #1 : Squaring / Square Roots / Radicals

Which of the following expressions is equal to the following expression?

\displaystyle \sqrt{(27)(45)(125)}

Possible Answers:

\displaystyle 225\sqrt{3}

\displaystyle 135\sqrt{5}

\displaystyle 125\sqrt{27}

\displaystyle 205\sqrt{3}

\displaystyle 75\sqrt{20}

Correct answer:

\displaystyle 225\sqrt{3}

Explanation:

\displaystyle \sqrt{(27)(45)(125)}

First, break down the component parts of the square root:

\displaystyle \sqrt{(3^{3})(5\times 3^{2})(5^{3})}

Combine like terms in a way that will let you pull some of them out from underneath the square root symbol:

\displaystyle \sqrt{(5^{4})(3^4)(3)}

Pull out the terms with even exponents and simplify:

\displaystyle (5^{2})(3^{2})\sqrt{3}=225\sqrt{3}

Example Question #1 : Complex Numbers

From \displaystyle \frac{3}{2} + \frac{1}{4} i, subtract its complex conjugate. What is the difference ?

Possible Answers:

\displaystyle 3

\displaystyle \frac{1}{2} i

\displaystyle -3

\displaystyle -\frac{1}{2} i

\displaystyle \frac{7}{4} + \frac{7}{4} i

Correct answer:

\displaystyle \frac{1}{2} i

Explanation:

The complex conjugate of a complex number \displaystyle a+bi is \displaystyle a - bi, so \displaystyle \frac{3}{2} + \frac{1}{4} i has \displaystyle \frac{3}{2} - \frac{1}{4} i as its complex conjugate. Subtract the latter from the former:

\displaystyle \left (\frac{3}{2} + \frac{1}{4} i \right ) - \left ( \frac{3}{2} - \frac{1}{4} i \right )

\displaystyle = \frac{3}{2} + \frac{1}{4} i - \frac{3}{2}+ \frac{1}{4} i

\displaystyle = \frac{3}{2}- \frac{3}{2} + \frac{1}{4} i + \frac{1}{4} i

\displaystyle = \frac{1}{2} i

Example Question #1 : How To Subtract Complex Numbers

From \displaystyle 17 - i \sqrt{17}, subtract its complex conjugate.

Possible Answers:

\displaystyle -34

\displaystyle - 2 i \sqrt{17}

\displaystyle 0

\displaystyle 34

\displaystyle 2 i \sqrt{17}

Correct answer:

\displaystyle - 2 i \sqrt{17}

Explanation:

The complex conjugate of a complex number \displaystyle a - bi is \displaystyle a+ bi. Therefore, the complex conjugate of \displaystyle 17 - i \sqrt{17} is \displaystyle 17 + i \sqrt{17}; subtract the latter from the former by subtracting real parts and subtracting imaginary parts, as follows:

\displaystyle (17 - i \sqrt{17})- (17 + i \sqrt{17})

\displaystyle = 17 - i \sqrt{17} - 17 - i \sqrt{17}

\displaystyle = 17 - 17 - i \sqrt{17} - i \sqrt{17}

\displaystyle = - 2 i \sqrt{17}

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