1(a)) Given that the map π : G → G defined by π(g) = g ∗ g.
"\\pi(g_1*g_2) = (g_1*g_2)* (g_1*g_2) = g_1*(g_2*g_1)*g_2" (because G is a group).
"= g_1*(g_1*g_2)*g_2" iff "(G,*)" is an abelian group
"\\implies \\pi(g_1*g_2) = (g_1*g_1)*(g_2*g_2) = \\pi(g_1)*\\pi(g_2)"
Thus, Given mapping is homomorphism if and only if G is abelian group.
1(b)) Given "P = \\{a_2 t\u00b2 + a_1 t + a_0 | a_2+ a_1 = a_0 \\ and \\ a_2, a_1, a_0 \\in \\R\\}" .
(i) Closure: Let A∈P,B∈P , so "A = a_2 t\u00b2 + a_1 t + a_0 , B = a_2' t\u00b2 + a_1' t + a_0'"
and "a_2+a_1=a_0, a_2'+a_1'=a_0'".
So, "(a_2+a_2')+(a_1+a_1') = a_0 +a_0'" and A+B∈P . Hence, Closure property holds.
(ii) Associative: Also, (A+B)+C=A+(B+C) ∀ A,B,C∈P .
Hence, Associativity property holds.
(iii) Identity: ∃ 0∈P:0+A=A for all A∈P . Hence, 0 is identity exists in P.
(iv) Inverse: "\\forall \\ A\\in P", ∃ B=−A∈P:A+B=0 .
Hence, the set P is group under addition.
1(c)) Given the set X = R\{−1} with the binary relation ∗ defined by x ∗ y = x + y + xy.
Now, "5 \u2217 x \u2217 2 = \u221219 \\implies (5+x+5x)*2 = -19"
"\\implies 5+x+5x+2+10+2x+10x = -19 \\\\\n\\implies 17+18x=-19 \\\\\n\\implies 18x = -36 \\\\\n\\implies x=-2"
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