Suppose $y = -1 - 2x$ - HSC - SSCE Mathematics Standard - Question 6 - 2020 - Paper 1

To determine how the value of $y$ changes when $x$ increases by 5, we first substitute $x$ with $x + 5$ in the original equation:

1. Original equation:
   $y = -1 - 2x$

2. New equation with x increased by 5:
   $y' = -1 - 2(x + 5)$
   This simplifies to:
   $y' = -1 - 2x - 10$
   $y' = -11 - 2x$

3. Change in y:
   The change in $y$ can be calculated as:
   $ext{Change in } y = y - y' = (-1 - 2x) - (-11 - 2x)$
   $= -1 - 2x + 11 + 2x$
   $= 10$

Thus, when $x$ increases by 5, the value of $y$ decreases by 10. Therefore, the answer is D. 10.