Question

Evaluate the expression 4y^2 -a if x = 2, y = -3, and a =6

Answer 1

The expression is telling you to proceed as follows:

• Pick some number
  `y`
• Pick some number
  `a`
• Compute the square of
  `y`
• Multiply it by 4
• Subtract
  `a` from this result.

So, first of all, there's no point in fixing
`x = 2`, because x doesn't appear in the expression. As for the evaluation, let's follow the aforementioned steps with fixed values:

Pick some number
`y`

• Pick
  `y=-3`
• Pick
  `a=6`
• Compute
  `y^2 = (-3)^2 = 9`
• Multiply it by 4:
  `9 \cdot 4 = 36`
• Subtract
  `6` from this result:
  `36-6=30`