Select the expressions that are equivalent to – 2(7a–1)–3a.

1) -2(-9a+16a-1)-3a
2)-2(-1+7a)-3a
3) -2(3a+4a-1)-3a
4)-17a+2

1 answer

To determine which expressions are equivalent to \(-2(7a-1)-3a\), we will simplify the original expression and then each of the options.

  1. Original expression: \[ -2(7a - 1) - 3a = -2 \cdot 7a + 2 \cdot 1 - 3a = -14a + 2 - 3a = -14a - 3a + 2 = -17a + 2 \]

Now let's simplify each of the options:

  1. \(-2(-9a + 16a - 1) - 3a\): \[ -2(-9a + 16a - 1) = -2(7a - 1) = -2 \cdot 7a + 2 \cdot 1 = -14a + 2 \] Then subtracting \(3a\): \[ -14a + 2 - 3a = -14a - 3a + 2 = -17a + 2 \]

  2. \(-2(-1 + 7a) - 3a\): \[ -2(-1 + 7a) = -2 \cdot (-1) + -2 \cdot (7a) = 2 - 14a \] Then subtracting \(3a\): \[ 2 - 14a - 3a = 2 - 17a \]

  3. \(-2(3a + 4a - 1) - 3a\): \[ -2(3a + 4a - 1) = -2(7a - 1) = -14a + 2 \] Then subtracting \(3a\): \[ -14a + 2 - 3a = -14a - 3a + 2 = -17a + 2 \]

  4. \(-17a + 2\): This expression is already in the form we derived earlier.

Now, let's compare the results:

  • Option 1: \(-17a + 2\) (equivalent to original)
  • Option 2: \(2 - 17a\) (not equivalent)
  • Option 3: \(-17a + 2\) (equivalent to original)
  • Option 4: \(-17a + 2\) (equivalent to original)

Thus, the equivalent expressions are: 1, 3, and 4.