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1: P(x)=M(x)+N(x)
=-2x^3+x^2+4x-3+2x^3+x^2-4x-5
=2x^2-8
2: P(x)=0
=>x^2-4=0
=>x=2 hoặc x=-2
3: Q(x)=M(x)-N(x)
=-2x^3+x^2+4x-3-2x^3-x^2+4x+5
=-4x^3+8x+2
b) Ta có:
P(x) + H(x) = x4 - x3 + 2x2 + x + 1
=> H(x) = x4 - x3 + 2x2 + x + 1 - P(x)
=> H(x) = (x4 - x3 + 2x2 + x + 1) - (2x4 - x2 + x - 2)
=> H(x) = -x4 - x3 + 3x2 + 3
Vậy H(x) = -x4 - x3 + 3x2 + 3
`a,`
`P(x)=2x^3-2x+x^2-x^3+3x+2`
`= (2x^3-x^3)+x^2+(-2x+3x)+2`
`= x^3+x^2+x+2`
`b,`
`H(x)+Q(x)=P(x)`
`-> H(x)=P(x)-Q(x)`
`-> H(x)=(x^3+x^2+x+2)-(x^3-x^2-x+1)`
`H(x)=x^3+x^2+x+2-x^3+x^2+x-1`
`= (x^3-x^3)+(x^2+x^2)+(x+x)+(2-1)`
`= 2x^2+2x+1`
Vậy, `H(x)=2x^2+2x+1.`
a.
\(P\left(x\right)=x^3+x^2+x+2\)
\(Q\left(x\right)=x^3-x^2-x+1\)
b.
\(H\left(x\right)+Q\left(x\right)=P\left(x\right)\Rightarrow H\left(x\right)=P\left(x\right)-Q\left(x\right)\)
\(\Rightarrow H\left(x\right)=x^3+x^2+x+2-\left(x^3-x^2-x+1\right)\)
\(\Rightarrow H\left(x\right)=2x^2+2x+1\)
Lời giải:
a)
$P(x)+Q(x)=4x^2+x-5+5x^3-2x^2+2x-1=5x^3+2x^2+3x-6$
b)
$H(x)=P(x)+ax=4x^2+x-5+ax=4x^2+x(a+1)-5$
c) Để $H(x)$ có nghiệm $x=2$
$\Leftrightarrow H(2)=0$
$\Leftrightarrow 4.2^2+2(a+1)-5=0$
$\Leftrightarrow a=\frac{-13}{2}$
Chọn C
Ta có: P(x) + Q(x) = x3+ x2+ 2x-1
⇒ Q(x) = (x3 + x2 + 2x-1) - P(x)
= 2x3 + 4x2 - 8x - 3.
`@` `\text {Ans}`
`\downarrow`
`a)`
Thu gọn:
`P(x)=`\(5x^4 + 3x^2 - 3x^5 + 2x - x^2 - 4 +2x^5\)
`= (-3x^5 + 2x^5) + 5x^4 + (3x^2 - x^2) + 2x - 4`
`= -x^5 + 5x^4 + 2x^2 + 2x - 4`
`Q(x) =`\(x^5 - 4x^4 + 7x - 2 + x^2 - x^3 + 3x^4 - 2x^2\)
`= x^5 + (-4x^4 + 3x^4) - x^3 + (x^2 - 2x^2) + 7x - 2`
`= x^5 - x^4 - x^3 - x^2 + 7x - 2`
`@` Tổng:
`P(x)+Q(x)=`\((-x^5 + 5x^4 + 2x^2 + 2x - 4) + (x^5 - x^4 - x^3 - x^2 + 7x - 2)\)
`= -x^5 + 5x^4 + 2x^2 + 2x - 4 + x^5 - x^4 - x^3 - x^2 + 7x - 2`
`= (-x^5 + x^5) - x^3 + (5x^4 - x^4) + (2x^2 - x^2) + (2x + 7x) + (-4-2)`
`= 4x^4 - x^3 + x^2 + 9x - 6`
`@` Hiệu:
`P(x) - Q(x) =`\((-x^5 + 5x^4 + 2x^2 + 2x - 4) - (x^5 - x^4 - x^3 - x^2 + 7x - 2)\)
`= -x^5 + 5x^4 + 2x^2 + 2x - 4 - x^5 + x^4 + x^3 + x^2 - 7x + 2`
`= (-x^5 - x^5) + (5x^4 + x^4) + x^3 + (2x^2 + x^2) + (2x - 7x) + (-4+2)`
`= -2x^5 + 6x^4 + x^3 + 3x^2 - 5x - 2`
`b)`
`@` Thu gọn:
\(H (x) = ( 3x^5 - 2x^3 + 8x + 9) - ( 3x^5 - x^4 + 1 - x^2 + 7x)\)
`= 3x^5 - 2x^3 + 8x + 9 - 3x^5 + x^4 - 1 + x^2 - 7x`
`= (3x^5 - 3x^5) + x^4 - 2x^3 - x^2 + (8x + 7x) + (9+1)`
`= x^4 - 2x^3 - x^2 + 15x + 10`
\(R( x) = x^4 + 7x^3 - 4 - 4x ( x^2 + 1) + 6x\)
`= x^4 + 7x^3 - 4 - 4x^3 - 4x + 6x`
`= x^4 + (7x^3 - 4x^3) + (-4x + 6x) - 4`
`= x^4 + 3x^3 + 2x - 4`
`@` Tổng:
`H(x)+R(x)=` \((x^4 - 2x^3 - x^2 + 15x + 10)+(x^4 + 3x^3 + 2x - 4)\)
`= x^4 - 2x^3 - x^2 + 15x + 10+x^4 + 3x^3 + 2x - 4`
`= (x^4 + x^4) + (-2x^3 + 3x^3) - x^2 + (15x + 2x) + (10-4)`
`= 2x^4 + x^3 - x^2 + 17x + 6`
`@` Hiệu:
`H(x) - R(x) =`\((x^4 - 2x^3 - x^2 + 15x + 10)-(x^4 + 3x^3 + 2x - 4)\)
`=x^4 - 2x^3 - x^2 + 15x + 10-x^4 - 3x^3 - 2x + 4`
`= (x^4 - x^4) + (-2x^3 - 3x^3) - x^2 + (15x - 2x) + (10+4)`
`= -5x^3 - x^2 + 13x + 14`
`@` `\text {# Kaizuu lv u.}`
a, P(x) = 3x\(^2\) + 2x\(^2\) -2x + 7 - x\(^2\) - x
= \((3x^2+2x^2-x^2)\) + (-2x - x) + 7
= 4x\(^2\) - 3x + 7
Q(x)=-3x\(^3\) + x - 14 - 2x - x\(^2-1\)
= -3x\(^3\) + (x-2x) +(-14-1) - x\(^2\)
= -3x\(^3\) - x - 15 - x\(^2\)
b, N(x)=P(x)-Q(x) =(4x\(^2\)-3x+7)-(-3x
-x-15-x)
= 4x\(^2\)-3x+7 + 3x\(^3\)+x+15+x\(^2\)
= (4x\(^2+x^2\)) + (\(-3x+x\))+(7+15)+3x\(^3\)
= \(5x^2\) - 2x + 12 +3x\(^3\)
M(x)=P(x)+Q(x)
=(4x\(^2\)-3x+7)+(-3x\(^3\)-x-15-x\(^2\))
=4x\(^2\)-3x+7-3x\(^3\)-x-15-x\(^2\)
=(4x\(^2\)-\(x^2\)) + (-3x-x) + (7-15)-3x\(^3\)
= 3 \(x^2\) - 4x - 8 -3x\(^3\)