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a) \(P\left(x\right)=3x^3-2x+2x^2+7x+8-x^4)\)

   \(P\left(x\right)=3x^3(-2x+7x)+2x^2+8-x^4)\)

   \(P\left(x\right)=3x^3+5x+2x^2+8-x^4)\)

   \(P\left(x\right)=-x^4+3x^3+2x^2+5x+8\)

 

  \(Q\left(x\right)=2x^2-3x^3+3x^2-5x^4\)

  \(Q\left(x\right)=(2x^2+3x^2)-3x^3-5x^4\)

  \(Q\left(x\right)=5x^2-3x^3-5x^4\)

  \(Q\left(x\right)=-5x^4-3x^2+5x^2\)

b)

\(P\left(x\right)+Q\left(x\right)=(3x^3-2x+2x^2+7x+8-x^4)+\left(2x^2-3x^3+3x^2-5x^4\right)\)

\(P\left(x\right)+Q\left(x\right)=3x^3-2x+2x^2+7x+8-x^4+2x^2-3x^3+3x^2-5x^4\)

\(P\left(x\right)+Q\left(x\right)=\left(3x^3-3x^3\right)+\left(-2x+7x\right)+\left(2x^2+2x^2+3x^2\right)+8+\left(-x^4-5x^4\right)\)\(P\left(x\right)+Q\left(x\right)=5x+7x^2+8-6x^4\)

Vậy: \(R\left(x\right)\) \(=5x+7x^2+8-6x^4\)

c. \(R\left(x\right)\) \(=5x+7x^2+8-6x^4\)

\(=5x+7x^2+4+4-6x^4\)

\(=\) \((12x-4)^2+4\ge4-6x^4\)

Câu c MIK KHÔNG CHẮC LÀ ĐÚNG 

26 tháng 11 2021

ko biết

Câu a :

\(\left(2x+1\right)^2-4x\left(x-5\right)\)

\(=4x^2+4x+1-4x^2+20\)

\(=4x+19\)

Câu b :

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

\(=x^2+6x+9-x^2-1\)

\(=6x-8\)

Câu c :

\(\left(x-5\right)^2-\left(x+2\right)^2\)

\(=\left(x-5-x-2\right)\left(x-5+x+2\right)\)

\(=-7\left(2x-3\right)\)

1 tháng 9 2017

Bạn trình bày cho rõ ràng xem nào.

3 tháng 8 2018

a) (x+2)(x-2) - (x-2)(x+5 )

= (x-2) (x+2 - x-5)

= -3 (x-2)

c) \(\left(3x+1\right)^2\) - \(\left(1-2x\right)^2\)

= (3x+1 - 1 +2x) (3x+1 +1-2x)

= 5x (x +2)

d) \(x^2\) - 4 - \(\left(x+2\right)^2\)

= (\(x^2\) - 4 ) - ( x+2) (x+2)

= (x-2) (x+2) - (x+2) (x+2)

= (x+2) (x-2 - x-2)

= -4 (x+2)

e: \(=x^2-16-2x^2-6x+x^2+6x+9=-7\)

b: \(=\left(6x+1-6x+1\right)^2=2^2=4\)

27 tháng 6 2017

\(\left(-x\right)\left(x^2-x+1\right)+\dfrac{1}{2}x^2\left(2x-4\right)+x\cdot x+x\cdot1-2\)

\(=-x^3+x^2-x+x^3-2x^2+x^2+x-2\)

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

\(=-2\)

28 tháng 6 2017

Thanks nha

5 tháng 8 2021

a)x²−2x−4y²−4ya)x²-2x-4y²-4y

=x²−2x−4y²−4y+2xy−2xy=x²-2x-4y²-4y+2xy-2xy

=(x²−2xy−2x)+(2xy−4y²−4y)=(x²-2xy-2x)+(2xy-4y²-4y)

=x(x−2y−2)+2y(x−2y−2)=x(x-2y-2)+2y(x-2y-2)

=(x+2y)(x−2y−2)=(x+2y)(x-2y-2)

b)x4+2x³−4x−4b)x4+2x³-4x-4

=x4+2x³+2x²−2x²−4x−4=x4+2x³+2x²-2x²-4x-4

=(x4+2x³+2x²)−(2x²+4x+4)=(x4+2x³+2x²)-(2x²+4x+4)

=x²(x²+2x+2)−2(x²+2x+2)=x²(x²+2x+2)-2(x²+2x+2)

=(x²−2)(x²+2x+2)=(x²-2)(x²+2x+2)

c)x³+2x²y−x−2yc)x³+2x²y-x-2y

=x²(x+2y)−(x+2y)=x²(x+2y)-(x+2y)

=(x²−1)(x+2y)=(x²-1)(x+2y)

=(x+1)(x−1)(x+2y)=(x+1)(x-1)(x+2y)

d)3x²−3y²−2(x−y)²d)3x²-3y²-2(x-y)²

=3(x²−y²)−2(x−y)²=3(x²-y²)-2(x-y)²

=3(x+y)(x−y)−2(x−y)²=3(x+y)(x-y)-2(x-y)²

=(x−y)[3(x+y)−2(x−y)]=(x-y)[3(x+y)-2(x-y)]

=(x−y)(3x+3y−2x+2y)=(x-y)(3x+3y-2x+2y)

=(x−y)(x+5y)=(x-y)(x+5y)

e)x³−4x²−9x+36e)x³-4x²-9x+36

=(x³−4x²)−(9x−36)=(x³-4x²)-(9x-36)

=x²(x−4)−9(x−4)=x²(x-4)-9(x-4)

=(x−4)(x²−9)=(x-4)(x²-9)

=(x−4)(x²−3²)=(x-4)(x²-3²)

=(x−4)(x+3)(x−3)=(x-4)(x+3)(x-3)

f)x²−y²−2x−2yf)x²-y²-2x-2y

=(x²−y²)−(2x+2y)=(x²-y²)-(2x+2y)

=(x+y)(x−y)−2(x+y)=(x+y)(x-y)-2(x+y)

=(x+y)(x−y−2)

hok tốt nhé

k đi