Simplify 3x(4x-5)+3 and find its value for (i) x=3 (ii) x=12. Simplify a(a²+a+1)+5 and find its value for (i) a=0 (ii) a=1 (iii) a=-5

[a] (i) 3x(4x-5)+3 = 3×3(4×3-5)+3 = 9(7)+3 = 66
(ii) 3x(4x-5)+3 = 3×12(4×12-5)+3 = 36(43)+3 = 1548+3 = 1551
[b] (i) a(a²+a+1)+5 = 0+5 = 5
(ii) a(a²+a+1)+5 = 1(3)+5 = 8
(iii) a(a²+a+1)+5 = -5(25-5+1)+5 = -5(21)+5 = -105+5 = -100