Question

4(a2 + 2b) - 2b when a = 2 and b = –2.

Answer 1

4

Keys:

• 
  `a \cdot (-b) = -a \cdot b`
• 
  `-\left(-a\right)=+a`

Explanation:

`4\left(\left(2\right)\cdot \:2+2\left(-2\right)\right)-2\left(-2\right)\\\left(2\right)\cdot \:2+2\left(-2\right)\\=4+2\left(-2\right)\\=4-4\\=0`

`=4\cdot \:0-2\left(-2\right)\\4\cdot \:0\\=0\\=0-2\left(-2\right)`

`2\left(-2\right)\\=-4\\=0-\left(-4\right)`

`0-\left(-4\right)\\=0+4\\=4`