Đáp án đúng phải là

\(h\left(x\right)=2x^5+5x^4+x^3-x^2-3x+6\)

1) 30x-30x^2-31

2)6x^4-2x^3-15x^2+23x-6

$\textbf{1)}$

$(3x-5)(7-5x)-(5x+2)(2-3x)$

$=(21x-15x^2-35+25x)-(10x-15x^2+4-6x)$

$=-15x^2+46x-35+15x^2-4x-4$

$=42x-39$

$=3(14x-13).$

a/ P(x) = x - 2\(x^2+3x^{^{ }5}+x^4+x-1\)

= \(3x^5+x^4-2x^{^{ }2}+\left(x+x\right)-1\)

= 3\(x^{^{ }5}+x^4-2x^2+2x-1\)

Q(x) = \(-3x^5+3x^{^{ }4}+2x^2-2x+3\)

b/ P(x) = 3\(x^5+x^4-2x^{^{ }2}+2x-1\)

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

P(x) +Q(x) = 4\(x^4+2\)

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

P(x)-Q(x) = (3x²-5+x⁴-3x³-x⁶-2x²-x³)-(x³+2x⁵x⁴+x²- 2x³+x-1 ) = \(3x^2-5+x^4-3x^3-x^6-2x^2-x^3-x^3-2x^5+x^4-x^2+2x^3-x+1=\left(3x^2-2x^2-x^2\right)+\left(x^4+x^4\right)+\left(-3x^3-x^3-x^3+2x^3\right)+\left(-5+1\right)-x^6-2x^5-x=2x^4-3x^3-4-x^6-2x^5-x\)=) hơi rắc rối nhé

a: \(=\left(x^7+x^7\right)+\left(-3x^4-x^4\right)+\left(2x^3-x^3\right)-x^2-x+5\)

\(=2x^7-4x^4+x^3-x^2-x+5\)

b: \(=-4x^5-3x^4+\left(2x^2-3x^2-x^2\right)-\dfrac{1}{2}x+1\)

\(=-4x^5-3x^4-2x^2-\dfrac{1}{2}x+1\)

a) \(A\left(x\right)=4x^5-2x^4+3x^2+5x-7\)

\(B\left(x\right)=-4x^5+2x^4+x^2+2x-12\)

hơi lười :((

b) \(A\left(x\right)+B\left(x\right)\\ =\left(4x^5-2x^4+3x^2+5x-7\right)+\left(-4x^5+2x^4+x^2+2x-12\right)\\ =4x^5-2x^4+3x^2+5x-7-4x^5+2x^4+x^2+2x-12\\ =\left(4x^5-4x^5\right)+\left(-2x^4+2x^4\right)+\left(3x^2+x^2\right)+\left(5x+2x\right)+\left(-7-12\right)\\ =4x^2+7x-19\)

\(A\left(x\right)-B\left(x\right)\\ =\left(4x^5-2x^4+3x^2+5x-7\right)-\left(-4x^5+2x^4+x^2+2x-12\right)\\ =4x^5-2x^4+3x^2+5x-7-4x^5-2x^4-x^2-2x+12\\ =\left(4x^5-4x^5\right)+\left(-2x^4-2x^4\right)+\left(3x^2-x^2\right)+\left(5x-2x\right)+\left(-7+12\right)\\ =-4x^4+2x^2+3x+5\)

\(3x^4+2x^3-x^2-3x^4+x^3+x^2-3x+5\)

\(=\left(3-3\right)x^4+\left(2+1\right)x^3-\left(1+1\right)x^2-3x+5\)

\(=0x^4+3x^3-0x^2-3x+5\)

\(=3x^3-3x+5\)

LG :

3x⁴ + 2x³ - x² - 3x⁴ + x³ + x² - 3x + 5 

= ( 3x⁴ - 3x⁴) + ( 2x³ + x³ ) + ( -x² + x² ) - 3x + 5

= 3x³ - 3x + 5

Hok tôt !!!    ^_^

a) M(x) + N(x) + P(x) = x⁵ + 7x⁴ - 6x³ - 3x² + x - 4