LearnAlgebra foundationsParentheses

Lesson notes
Problem set 0.1
Problem set 1
Problem set 2
Problem set 3
Problem set 4
Problem set 5
Problem set 6
Problem set 7
Problem set 8
Problem set 9
Problem set 10
Problem set 11
Problem set 12
Problem set 13
Problem set 14


Lesson notes

  • Purpose of using parentheses is to group parts of an expressions into whole units.
  • In each step of algebra work, ask yourself if parentheses need to be added to group parts of an expression into whole units.
    • For example, if we want to evaluate x^2+1 when x = -1, we note that x should be getting squared and whatever we put in place of x as a whole must be squared. So, x^2+1 would evaluate to (-1)^2+1, not -1^2+1.
    • As a second example, if z = y^2 and y = x+2, and we want to express z in terms of x, we write z = (x+2)^2, not z = x+2^2. Again, this is because in evaluating z = y^2, whatever comes in place of y, in this case x+2, as a whole must be squared.
    • As another example, \frac{a}{2} - \frac{a+1}{2} is equal to \frac{a-(a+1)}{2}, not \frac{a-a+1}{2}. This is because in \frac{a}{2} - \frac{a+1}{2}, the second fraction is being subtracted, and when we subtract the numerator of the second fraction from the first, we need to subtract the whole of the second fraction’s numerator.
    • Sometimes, grouping of a part of an expression into a whole comes for free because of PEMDAS. For example, if z = 3+y and y = 2\times x, and we want to express z in terms of x, we just say z = 3+2\times x. Here, there is no reason to use parentheses around 2\times x when replacing y in z = 3+y because PEMDAS ensures 2\times x is evaluated first and then 3 is added in evaluating 3+2\times x.


Problem set 0.1

For each of the following, get rid of parentheses appropriately and simplify.

  1. -(a)
  2. -(-x)


Problem set 1

For each of the following, get rid of parentheses appropriately and simplify.

  1. (a+b)+(c+d)
  2. (p+q+r)+(s+t)
  3. (p-q+r)+(s-t)
  4. (p-r)+(r-q-p)
  5. (-a-b)+(a-b-c)


Problem set 2

For each of the following, get rid of parentheses appropriately and simplify.

  1. a-(b-c)
  2. -a-(b-c)
  3. -a-(-b+c)
  4. (b-c)-a
  5. (-b+c)-a


Problem set 3

For each of the following, get rid of parentheses appropriately and simplify.

  1. -2(-b)
  2. a-5(-b)
  3. x-2(-3x)
  4. x+2-2(-3x)
  5. 3x+2-3(-2x+7)


Problem set 4

For each of the following, get rid of parentheses appropriately and simplify.

  1. (a+b)+2(c+d)
  2. 3(p-q+r)-(q-r)
  3. -(p-q+r)-2(p-r)
  4. -3(p-q)-3(p-q-r)
  5. 3(-a-b)-3(a-c-b)


Problem set 5

For each of the following, get rid of parentheses appropriately and simplify.

  1. (a\times b)\times(c\times d\times e)
  2. (-a)(b-c)
  3. (a-b)(-c)
  4. (a)(-c)
  5. (ab)(-cd)


Problem set 6

Which of the following are true? Justify with reasons.

  1. (a+b)^2 = a+b^2
  2. ab^2 = ab\times ab
  3. (-a)^2 = (-a)\times (-a)
  4. (a+b)^2 = a+b\times a+b
  5. (a-b)^2 = a-b\times a-b
  6. (a+b)\times 2 = a+b\times 2
  7. 3x^2 = 9\times x^2
  8. -a^2 = a^2
  9. (-a)^2 = a^2


Problem set 7

Which of the following are true? Justify with reasons.

  1. a(-b-c)  = a-b-c
  2. a(-b)  = a-b
  3. (ab)(-cd) = ab-cd
  4. (abc)(-d)  = -abcd
  5. (abc)-d  = abc-d
  6. 2(abc)  = 2a2b2c
  7. -(xyz)  = -x-y-z


Problem set 8

Which of the following are true? Justify with reasons.

  1. a + (b\times c)  = a+b\times c
  2. (a + b)\times c  = a+b\times c
  3. a + \left(\frac{b}{c}\right)  = a+\frac{b}{c}
  4. a \times \left(\frac{b}{c}\right)  = a\times\frac{b}{c}
  5. \left(\frac{a}{b}\right) \times \left(\frac{c}{d}\right)  = \frac{a}{b}\times\frac{c}{d}
  6. (ab)^2 = ab^2
  7. \left(\frac{a}{b}\right)^2 = \frac{a^2}{b}


Problem set 9

Which of the following are true? Justify with reasons.

  1. x+1\times 2 = 2x+2
  2. x+1\times 5x-1 = 6x-1
  3. 1-3x\times 2-6x = -12x+1


Problem set 10

For each of the following problems, assume what is given and express z in terms of x.

  1. z = 1-y and y = 2\times x
  2. z = 3+y and y = 2 + x
  3. z = 1+2y and y = x+2
  4. z = 1-y and y = 3x+1
  5. z = 3x+1-2y and y = 3x+1


Problem set 11

Simplify each of the following as possible.

  1. 2x^2
  2. (2x)^2
  3. (-2x)^2
  4. ab^2
  5. (ab)^2
  6. (-ab)^2
  7. \left(\frac{x}{2}\right)^2
  8. \frac{x^2}{2}


Problem set 12

For each of the following problems, assume what is given and express z in terms of x.

  1. z = 1+y^2 and y = -x
  2. z = 1-2y^2 and y = -x
  3. z = 1+y^2 and y = 2x
  4. z = 1-y^2 and y = -2x
  5. z = 1-2y^3 and y = -x
  6. z = 1+y^2 and y = x+1


Problem set 13

Simplify each of the following.

  1. \frac{2}{7}\times\frac{3x+3}{5}
  2. \frac{a}{2} - \frac{a+2}{2}
  3. -\frac{x+2}{x+3}\times (-1)
  4. \frac{x}{3} - \frac{3-x}{3}
  5. \frac{x+5}{x+3} - \frac{x+5}{x+3}
  6. \frac{x^2-2x-5}{x+3} - \frac{x^2+2x-5}{x+3}


Problem set 14

Which of the following are true? Justify with reasons.

  1. -\frac{2x+5}{x+3} = \frac{-2x+5}{x+3}
  2. -\frac{x+2}{x+3} = \frac{-x-2}{x+3}
  3. (x+5)\times\frac{2x+1}{x+5} = 2x+1
  4. (1-5x)\times\frac{x^2-4}{1-5x} = x^2-4
  5. x+2\times\frac{3}{x+2} = 3
  6. 2x-2\times\frac{x+5}{2x-2} = x+5