Exercicios:
a) $7 x z^{2} y+10 x z y^{2}-3 x^{2} z y+3 x z y^{2}-7 x z^{2} y+15 x^{2} z y$
b) $9 a^{4}+10 a^{3}+11 a^{2}-8 a^{4}+10 a^{2}-10 a^{3}+20 a$
c) $a b+a c+a d+a f-a d-a c+a f-a b$
c) \(\boxed{2 a f}\)
Step 1 :Simplify the given expressions by combining like terms:
Step 2 :a) $7 x z^{2} y+10 x z y^{2}-3 x^{2} z y+3 x z y^{2}-7 x z^{2} y+15 x^{2} z y$
Step 3 :b) $9 a^{4}+10 a^{3}+11 a^{2}-8 a^{4}+10 a^{2}-10 a^{3}+20 a$
Step 4 :c) $a b+a c+a d+a f-a d-a c+a f-a b$
Step 5 :Simplify each expression:
Step 6 :a) $x y z (12 x + 13 y)$
Step 7 :b) $a (a^3 + 21 a + 20)$
Step 8 :c) $2 a f$
Step 9 :\(\boxed{\text{Final Answer:}}\)
Step 10 :a) \(\boxed{x y z (12 x + 13 y)}\)
Step 11 :b) \(\boxed{a (a^3 + 21 a + 20)}\)
Step 12 :c) \(\boxed{2 a f}\)