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a, Sắp xếp : \(P\left(x\right)=2x^3+5x^2-3x^4+7-4x\)
\(\Rightarrow P\left(x\right)=-3x^4+2x^3-5x^2-4x+7\)
\(Q\left(x\right)=-3+2x^4-x+x^3-5x^2\)
\(\Rightarrow Q\left(x\right)=2x^4+x^3-5x^2-x-3\)
b, Ta có :* Đặt \(V\left(x\right)=P\left(x\right)+Q\left(x\right)\)
hay \(V\left(x\right)=2x^3+5x^2-3x^4+7-4x-3+2x^4-x+x^3-5x^2\)
\(=3x^3-x^4+4-5x\)
Vậy \(V\left(x\right)=3x^3-x^4+4-5x\)
Ta có : * Đặt \(K\left(x\right)=P\left(x\right)-Q\left(x\right)\)
hay \(2x^3+5x^2-3x^4+7-4x-\left(-3+2x^4-x+x^3-5x^2\right)\)
\(=2x^3+5x^2-3x^4+7-4x+3-2x^4+x-x^3+5x^2\)
\(=x^3+10x^2-5x^4+10-3x\)
Vậy \(K\left(x\right)=x^3+10x^2-5x^4+10-3x\)
\(P\left(x\right)=-4x^4+3x^3+4x^2+3x+6\)
\(Q\left(x\right)=-x^5+2x^4-2x^3+3x^2-x+\frac{1}{4}\)
\(P\left(x\right)+Q\left(x\right)=-x^5-2x^4+x^3+7x^2+2x+\frac{25}{4}\)
\(P\left(x\right)-Q\left(x\right)=x^5-6x^4+5x^3+x^2+4x+\frac{23}{4}\)
P(x) = -4x^4 + (5x^3 - 2x^3) + 4x^2 + 3x + 6
= -4x^4 + 3x^3 + 4x^2 + 3x + 6
Q(x) = -x^5 + 2x^4 - 2x^3 + 3x^2 - x + 1/4
P(x) + Q(x) = (-4x^4 + 3x^3 + 4x^2 + 3x + 6) + (-x^5 + 2x^4 - 2x^3 + 3x^2 - x + 1/4)
= -4x^4 + 3x^3 + 4x^2 + 3x + 6 - x^5 + 2x^4 - 2x^3 + 3x^2 - x + 1/4
= -x^5 - (4x^4 - 2x^4) + (3x^3 - 2x^3) + (4x^2 + 3x^2) + (3x - x) + (6 + 1/4)
= -x^5 - 2x^4 + x^3 + 7x^2 + 2x + 25/4
P(x) - Q(x) = (-4x^4 + 3x^3 + 4x^2 + 3x + 6) - (-x^5 + 2x^4 - 2x^3 + 3x^2 - x + 1/4)
= -4x^4 + 3x^3 + 4x^2 + 3x + 6 + x^5 - 2x^4 + 2x^3 - 3x^2 + x - 1/4
= x^5 - (4x^4 + 2x^4) + (3x^3 + 2x^3) + (4x^2 - 3x^2) + (3x + x) + (6 - 1/4)
= x^5 - 6x^4 + 5x^3 + x^2 + 4x + 23/4
Chúc bạn học tốt
a, P(x)= 5+x\(^3\)-2x+4x\(^3\)+3x\(^2\)-10
=(5-10) + (x\(^3\) + 4x\(^3\)) - 2x + 3x\(^2\)
= -5 + 5x\(^3\) - 2x + 3x\(^2\)
sắp xếp : P(x) = -5 - 2x + 3x\(^2\) + 5x\(^3\)
Q(x)=4-5x\(^3\)+2x\(^2\)-x\(^3\)+6x+11x\(^3\)-8x
= 4 - (5x\(^3\)-x\(^3\)+11x\(^3\)) + 2x\(^2\) + (6x - 8x)
= 4 - 15x\(^3\) + 2x\(^2\) - 2x
Sắp xếp : Q(x) = 4 - 2x + 2x\(^2\) -15 x\(^3\)
b, P(x) + Q(x) = ( -5-2x+3x\(^2\)+5x\(^3\)) + (4-2x+2x\(^2\)-15x\(^3\))
= -5 -2x + 3x\(^2\) + 5x\(^3\) + 4 - 2x + 2x\(^2\) - 15x\(^3\)
= (-5 + 4) + (-2x-2x) + (3x\(^2\)+ 2x\(^2\)) + (5x\(^3\) - 15x\(^3\))
=- 1 -4x+ 5x\(^2\) - 10x\(^3\)
P(x) - Q(x) = (-5-2x+3x\(^2\)+5x\(^3\)) - (4-2x+2x\(^2\)-15x\(^3\))
= -5-2x+3x\(^2\)+5x\(^3\)- 4+2x-2x\(^2\)+15x\(^3\)
= (-5-4) + (-2x+2x) + (3x\(^2\)-2x\(^2\)) + (5x\(^3\)+15x\(^3\))
= -9 + x\(^2\) + 20x\(^3\)
a) \(P\left(x\right)=-3x^3+9-5x+7x^4-2x^2\)
\(=7x^4-3x^3-2x^2-5x+9\)
\(Q\left(x\right)=6x^2+5x-2x^4+8x^3-11\)
\(=-2x^4+8x^3+6x^2+5x-11\)
b) Ta có: \(P\left(x\right)+Q\left(x\right)\)
\(=\left(7x^4-3x^3-2x^2-5x+9\right)+\left(-2x^4+8x^3+6x^2+5x-11\right)\)
\(=7x^4-3x^3-2x^2-5x+9-2x^4+8x^{^3}+6x^2+5x-11\)
\(=\left(7x^4-2x^4\right)-\left(3x^3-8x^3\right)-\left(2x^2-6x^2\right)-\left(5x-5x\right)+\left(9-11\right)\)
\(=5x^4+5x^{^3}+4x^2 -2\)
Lại có: \(P\left(x\right)-Q\left(x\right)\)
\(=\left(7x^4-3x^3-2x^2-5x+9\right)-\left(-2x^4+8x^3+6x^2+5x-11\right)\)
\(=7x^4-3x^3-2x^2-5x+9+2x^4-8x^3-6x^2-5x+11\)
\(=\left(7x^4+2x^4\right)-\left(3x^3+8x^3\right)-\left(2x^2+6x^2\right)-\left(5x+5x\right)+\left(9+11\right)\)
\(=9x^4-11x^3-8x^2-10x+20\)