Answer:
a = -1
Step-by-step explanation:
The general equation for a straight line is y = mx+c, where m is the gradient/ slope, so m = -5. The first thing we need to do is find c, which we do by plugging in the x and y values that we already know: y = 7 and x = -2
7 = -5*(-2) + c
7 = 10 + c
c = 7-10 = -3
Now, we have the general equation of y = -5x -3 and we can use this to find a.
We'll treat a as x and y will be equal to 2:
2 = -5a -3
5 = -5a (Divide both sides by 5)
-a = 1 (now by -1)
a = -1
