Answer:
a = 3 and b = -10.5
Explanation:
We have the vector

First, this vector is dilated by a factor of 1.5
So, the new vector is,

i.e.

i.e.

Further, this vector is reflected across the x-axis.
So, the resulting vector is

Thus, the value of 'a' and 'b' are 3 and -10.5 respectively.