$\"\"$

The expression is $\"\"$ .

$\"\"$ (Substitute 4 for y and $\"\"$ for z)

Both have different signs, so subtract the lesser absolute value from greater absolute value.

$\"\"$ (Different signs: Subtract $\"\"$ from $\"\"$ )

$\"\"$ (Since $\"\"$ , the sum has the same sign as $\"\"$ ) $\"\"$

The expression is $\"\"$ .