a. To compute the convolution of x

and h

, we can use the formula for discrete convolution:
y

= x

* h

= Σ x(k) * h(n-k)
Given:
x

= {2, -4, 2}
h

= {7, 1, 4, -4, -4}
Let's find y

step by step:
n = 0: y(0) = 2 * 7 = 14
n = 1: y(1) = 2 * 1 + (-4) * 7 = 2 - 28 = -26
n = 2: y(2) = 2 * 4 + (-4) * 1 + 2 * 7 = 8 - 4 + 14 = 18
n = 3: y(3) = (-4) * 4 + 2 * 1 = -16 + 2 = -14
n = 4: y(4) = (-4) * 4 = -16
Therefore, the convolution of x

and h

is y

= {14, -26, 18, -14, -16}.
b. Given:
x

= {6, -6, -2, 3}
h

= {1, 0, -1, -1}
Let's find y

step by step:
n = 0: y(0) = 6 * 1 = 6
n = 1: y(1) = 6 * 0 + (-6) * 1 = 0 - 6 = -6
n = 2: y(2) = 6 * (-1) + (-6) * 0 + (-2) * 1 = -6 - 0 - 2 = -8
n = 3: y(3) = (-6) * (-1) + (-2) * 0 + 3 * 1 = 6 + 0 + 3 = 9
Therefore, the convolution of x

and h

is y

= {6, -6, -8, 9}.
c. Given:
x

= {1, 1, 2, 1, 1}
h

= {5, -9, -1, 4}
Let's find y

step by step:
n = 2: y(2) = 1 * 5 + 1 * (-9) = 5 - 9 = -4
n = 3: y(3) = 1 * (-9) + 2 * 5 + 1 * (-1) = -9 + 10 - 1 = 0
n = 4: y(4) = 2 * (-1) + 1 * 5 + 1 * (-9) = -2 + 5 - 9 = -6
n = 5: y(5) = 1 * 4 + 2 * (-1) + 1 * 5 = 4 - 2 + 5 = 7
n = 6: y(6) = 1 * 4 + 1 * (-1) = 4 - 1 = 3
Therefore, the convolution of x

and h

is y

= {0, -4, 0, -6, 7, 3}.