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a.Mik làm rồi nhé!
\(b.P\left(x\right)+Q\left(x\right)=\left(2x^2-x+5\right)+\left(-2x^2+4x-1\right)\\ =2x^2-x+5-2x^2+4x-1\\ =3x+4\\ ------\\ P\left(x\right)-Q\left(x\right)=\left(2x^2-x+5\right)-\left(-2x^2+4x-1\right)\\ =2x^2-x+5+2x^2-4x+1\\ =4x^2-5x+6\)
\(c.\)nghiệm của đa thức P(x) + Q(x)
\(3x+4=0\\ \Leftrightarrow3x=-4\\ \Leftrightarrow x=\dfrac{-4}{3}\)
\(\Leftrightarrow\)vậy...
a: \(M\left(x\right)=9x^4+2x^2-x-6\)
\(N\left(x\right)=-x^4-x^3-2x^2+4x+1\)
b: \(P\left(x\right)=8x^4-x^3+3x-5\)
\(Q\left(x\right)=10x^4+x^3+4x^2-5x-7\)
a: \(M\left(x\right)=9x^4+2x^2-x-6\)
\(N\left(x\right)=-x^4-x^3-2x^2+4x+1\)
b: \(P\left(x\right)=8x^4-x^3+3x-5\)
\(Q\left(x\right)=10x^4+x^3+4x^2-5x-7\)
`P(x)=x^2+5x^4-3x^2+x^2+4x^4+3x^3-x+5`
`=(5x^4+4x^4)+3x^3+(x^2-3x^2+x^2)-x+5`
`=9x^4+3x^3-x^2-x-5`
`Q(x)=x-5x^3-x^2-x^4+4x^3-x^2+3x-1`
`=-x^4+(4x^3-5x^3)-(x^2+x^2)+(x+3x)-1`
`=-x^4-x^3+4x-1`
`P(x)+Q(x)=9x^4+3x^3-x^2-x-5-x^4-x^3+4x-1`
`=(9x^4-x^4)+(3x^3-x^3)-x^2-(x-4x)-(5+1)`
`=8x^4+2x^3-x^2-5x-6`
`P(x)-Q(x)=9x^4+3x^3-x^2-x-5+x^4+x^3-4x+1`
`=(9x^4+x^4)+(3x^3+x^3)-x^2-(x+4x)-(5-1)`
`=10x^4+4x^3-x^2-5x-4`
a) Ta có: \(M\left(x\right)=3x^3+x^2+4x^4-x-3x^3+5x^4+2x^2-6\)
\(=\left(4x^4+5x^4\right)+\left(3x^3-3x^3\right)+\left(x^2+2x^2\right)-x-6\)
\(=9x^4+3x^2-x-6\)
Ta có: \(N\left(x\right)=-2x^2-x^4+4x^3-x^2-5x^3+3x+5+x\)
\(=-x^4+\left(4x^3-5x^3\right)+\left(-2x^2-x^2\right)+\left(3x+x\right)+5\)
\(=-x^4-x^3-3x^2+4x+5\)
c) Ta có: M(x)+N(x)
\(=9x^4+3x^2-x-6-x^4-x^3-3x^2+4x+5\)
\(=8x^4-x^3+3x-1\)
A(x) = x2 + 5x4 - 3x3 + x2 - 4x4 + 3x3 - x + 5
= ( 5x4 - 4x4 ) + ( 3x3 - 3x3 ) + ( x2 + x2 ) - x + 5
= x4 + 2x2 - x + 5
B(x) = x - 5x3 - x2 - x4 + 5x3 - x2 - 3x + 1
= -x4 + ( 5x3 - 5x3 ) + ( -x2 - x2 ) + ( -3x + x ) + 1
= -x4 - 2x2 - 2x + 1
M(x) = A(x) + B(x)
= x4 + 2x2 - x + 5 + ( -x4 - 2x2 - 2x + 1 )
= x4 + 2x2 - x + 5 - x4 - 2x2 - 2x + 1
= -3x + 6
N(x) = A(x) - B(x)
= x4 + 2x2 - x + 5 - ( -x4 - 2x2 - 2x + 1 )
= x4 + 2x2 - x + 5 + x4 + 2x2 + 2x - 1
= 2x4 + 4x2 + x + 4
M(x) = 0 <=> -3x + 6 = 0
<=> -3x = -6
<=> x = 2
Vậy nghiệm của M(x) là 2
;y=-1
; Q(x) = x2 – 9.; R(x) = 3x2 – 4x
)
21:
a: \(f\left(x\right)=4x^4-x^3-4x^2+x-1\)
\(g\left(x\right)=x^4+4x^3+x-5\)
b: f(x)-g(x)
=4x^4-x^3-4x^2+x-1-x^4-4x^3-x+5
=3x^4-5x^3-4x^2+4
f(x)+g(x)
=4x^4-x^3-4x^2+x-1+x^4+4x^3+x-5
=5x^4+3x^3-4x^2+2x-6
c: g(-1)=1-4-1-5=-9
a) Thu gọn và sắp xếp:
\(P\left(x\right)=x^2+5x^4-3x^3+x^2+4x^4+3x^3-x+5\)
\(P\left(x\right)=\left(5x^4+4x^4\right)-\left(3x^3-3x^3\right)+\left(x^2+x^2\right)-x+5\)
\(P\left(x\right)=9x^4+2x^2-x+5\)
\(Q\left(x\right)=x-5x^3-x^2-x^4+4x^3-x^2+3x-1\)
\(Q\left(x\right)=x^4-\left(5x^3-4x^3\right)-\left(x^2+x^2\right)+\left(x+3x\right)-1\)
\(Q=x^4-x^3-2x^2+4x-1\)
b) \(P\left(x\right)+Q\left(x\right)\)
\(=\left(9x^4+2x^2-x+5\right)+\left(x^4-x^3-2x^2+4x-1\right)\)
\(=9x^4+2x^2-x+5+x^4-x^3-2x^2+4x-1\)
\(=\left(9x^4+x^4\right)-x^3+\left(2x^2-2x^2\right)-\left(x-4x\right)+\left(5-1\right)\)
\(=10x^4-x^3+3x+4\)
\(P\left(x\right)-Q\left(x\right)\)
\(=\left(9x^4+2x^2-x+5\right)-\left(x^4-x^3-2x^2+4x-1\right)\)
\(=9x^4+2x^2-x+5-x^4+x^3+2x^2-4x+1\)
\(=\left(9x^4-x^4\right)+x^3+\left(2x^2+2x^2\right)-\left(x+4x\right)+\left(5-1\right)\)
\(=8x^4+x^3+4x^2-5x+4\)