I need some help w/ algebra

Multiply or divide. State any restrictions on the variables.

1. (4a^5)/(7b^4) * (2b^2)/(2a^4)

a. (4a^9)/(7b^6), a = 0, b = 0
b. (4a)/(7b^2), a = 0, b = 0
c. (7b^2)/(4a), a = 0, b = 0
d. 4/7a^9b^6, a = 0, b = 0

2. (z^2)/(z + 1) * (z^2 + 3z + 2)/(z^2 + 3z)

a. (z^2 + 2z)/(z + 3), z = -1, -3
b. (z + 2)/(z + 3), z = -1, 0, -3
c. (z + 2)/(z + 3), z = -1, -3
d. (z^2 + 2z)/(z + 3), z = -1, 0, -3

3. (c + 1)/(c - 5) divided by (c - 2)/(c^2 - 7c + 10)

a. [(c + 1)(c - 2)]/[(c - 5)^2(c - 2)], c = 5,2,2
b. [(c + 1)(c - 2)]/[(c - 2)], c = 5,2
c. [(c + 1)(c - 2)]/[(c - 2)], c = 2,2
d. [(c + 1)(c - 2)]/[(c - 5)^2(c - 2)], c = 5,2

1. (4a^5)/(7b^4) * (2b^2)/(2a^4)
Reduce by a factor of 2:
= (4a^5)/(7b^4) * (b^2)/(a^4)
The a^5 divided by (a^4) is a:
= (4a)/(7b^4) * (b^2)/(1)
Reduce b next:
= (4a)/(7b^2) * (1)/(1)
= (4a)/(7b^2)
b. (4a)/(7b^2), a = 0, b = 0

2. (z^2)/(z + 1) * (z^2 + 3z + 2)/(z^2 + 3z)
= (z^2)/(z + 1) * ((z + 2)(z + 1))/(z^2 + 3z)
= (z^2)/(z + 1) * ((z + 2)(z + 1))/(z*z + 3z)
= (z^2)/(z + 1) * ((z + 2)(z + 1))/(z(z + 3))
Now cancel common factors:
= (z)/(1) * ((z + 2)/((z + 3))
=z(z + 2) / (z + 3)
= (z^2 + 2z) / (z + 3)
d. (z^2 + 2z)/(z + 3), z = -1, 0, -3

3. (c + 1)/(c - 5) divided by (c - 2)/(c^2 - 7c + 10)
= ((c + 1)/(c - 5)) / ((c - 2)/(c^2 - 7c + 10))
= ((c + 1)/(c - 5)) / ((c - 2)/((c - 2)(c - 5)))
= ((c + 1)/(c - 5)) * ((c - 2)(c - 5))/(c - 2)
= ((c + 1)(c - 2)(c - 5)) / ((c - 2)(c - 5))
= c + 1
But doesn't match your answers.
So rewrite the previous line as:
= ((c + 1)(c - 2)) / (c - 2)
b. [(c + 1)(c - 2)]/[(c - 2)], c = 5,2