For the following exercises, perform the given operations and simplify.
35. \(\left(3 x^{3}+2 x-1\right)+\left(4 x^{2}-2 x+7\right)\)
36. \((2 y+1)-\left(2 y^{2}-2 y-5\right)\)
37. \(\left(2 x^{2}+3 x-6\right)+\left(3 x^{2}-4 x+9\right)\)
38. \(\left(6 a^{2}+3 a+10\right)-\left(6 a^{2}-3 a+5\right)\)
39. \((k+3)(k-6)\)
40. \((2 h+1)(3 h-2)\)
41. \((x+1)\left(x^{2}+1\right)\)
42. \((m-2)\left(m^{2}+2 m-3\right)\)
43. \((a+2 b)(3 a-b)\)
44. \((x+y)(x-y)\)