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Bài `2`

`a, P(x)=12-6x^3+9x-x^2`

`= -6x^3 -x^2 +9x+12`

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`Q(x)=4+10x^2+29x^3-6x`

`= 29x^3 +10x^2 -6x+4`

`b,P(x)+Q(x)= -6x^3 -x^2 +9x+12 + 29x^3 +10x^2 -6x+4`

`= (-6x^3+ 29x^3)+(-x^2+10x^2) +(9x -6x) +(12+4)`

`= 23x^3+ 9x^2 + 3x + 16`

`c,P(x)-Q(x)=(-6x^3 -x^2 +9x+12) - (29x^3 +10x^2 -6x+4)`

`= -6x^3 -x^2 +9x+12- 29x^3-10x^2 +6x-4`

`= (-6x^3- 29x^3 )+(-x^2-10x^2)+(9x+6x) +(12-4)`

`= -35x^3 -11x^2 + 15x + 8`

`2,`

`a, P(x)=12 - 6x^3+9x-x^2`

`P(x)= -6x^3 - x^2 + 9x +12`

`Q(x)=4+10x^2+29x^3-6x`

`Q(x)= 29x^3 +10x^2-6x+4`

`b, P(x)+Q(x)= (-6x^3-x^2+9x+12) + (29x^3+10x^2-6x+4)`

`P(x)+Q(x)= -6x^3-x^2+9x+12 + 29x^3+10x^2-6x+4`

`P(x)+Q(x)= (-6x^3+29x^3) - (x^2-10x^2)+(9x-6x)+(12+4)`

`P(x)+Q(x)=23x^3 + 8x^2+3x+16`

`c, P(x)-Q(x)= (-6x^3-x^2+9x+12) - (29x^3+10x^2-6x+4)`

`P(x)-Q(x)= -6x^3-x^2+9x+12 - 29x^3 - 10x^2+6x-4`

`P(x)-Q(x)= (-6x^3 - 29x^3) - (x^2+10x^2)+(9x+6x)+(12-4)`

`P(x)-Q(x)= -35x^3-11x^2+15x+8`

a: M(x)=3x^3-7x^2+4/5x-1/5

N(x)=3x^3-7x^2-x+3/2

b: M(x)+N(x)=6x^3-14x^2-1/5x+13/10

c: H(x)=M(x)-N(x)

=3x^3-7x^2+4/5x-1/5-3x^3+7x^2+x-3/2

=9/5x-17/10

2:

a: \(A\left(x\right)=3x^3-2x^2-5x+3\)

\(B\left(x\right)=5x^3+x^2+2x-1\)

b: A(x)+B(x)=8x^3-x^2-3x+2

c: A(x)-B(x)

=3x^3-2x^2-5x+3-5x^3-x^2-2x+1

=-2x^3-3x^2-7x+4

a/\(F\left(x\right)=-4x^2+7-6x+5x^3\)
\(=5x^3-4x^2-6x+7\)
\(G\left(x\right)=4x^2+9x-2x^4+4x^3-12\)
\(=-2x^4+4x^3+4x^2+9x-12\)
b/\(F\left(x\right)+G\left(x\right)=\left(5x^3-4x^2-6x+7\right)+\left(-2x^4+4x^3+4x^2+9x-12\right)\)
\(=5x^3-4x^2-6x+7-2x^4+4x^3+4x^2+9x-12\)
\(=\left(5x^3+4x^3\right)-\left(4x^2-4x^2\right)+\left(-6x+9x\right)-2x^4-\left(-7+12\right)\)
\(=9x^3-0+3x-2x^4-5\)
\(=9x^3+3x-2x^4-5\)

2:

1+cot^2a=1/sin^2a

=>1/sin^2a=1681/81

=>sin^2a=81/1681

=>sin a=9/41

=>cosa=40/41

tan a=1:40/9=9/40