Bài làm của bạn đây

giup e với

a)f(x)+g(x)=\(x^5-4x^4-2x^2-7-2x^5+6x^4-2x^2+6.\)

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

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

=\(3x^5-10x^4-13\)

b)f(x)+g(x)=\(5x^4+7x^3-6x^2+3x-7-4x^4+2x^3-5x^2+4x+5\)

=\(x^4+9x^3-11x^2+7x-2\)

f(x)-g(x)=\(5x^4+7x^3-6x^2+3x-7+4x^4-2x^3+5x^2-4x-5\)

=\(9x^4+5x^3-x^2-x-12\)

a ) 

\(f\left(x\right)+g\left(x\right)=x^5-4x^4-2x^2-7+-2x^5+6x^4-2x^2+6\)

\(\Rightarrow f\left(x\right)+g\left(x\right)=\left(x^5-2x^5\right)+\left(6x^4-4x^4\right)-\left(2x^2+2x^2\right)+\left(6-7\right)\)

\(\Rightarrow f\left(x\right)+g\left(x\right)=-x^5+2x^4-4x^2-1\)

\(f\left(x\right)-g\left(x\right)=x^5-4x^4-2x^2-7-\left(-2x^5+6x^4-2x^2+6\right)\)

\(\Rightarrow f\left(x\right)-g\left(x\right)=x^5-4x^4-2x^2-7+2x^5-6x^4+2x^2-6\)

\(\Rightarrow f\left(x\right)-g\left(x\right)=\left(x^5+2x^5\right)-\left(4x^4+6x^4\right)+\left(2x^2-2x^2\right)-\left(6+7\right)\)

\(\Rightarrow f\left(x\right)-g\left(x\right)=3x^5-10x^4-13\)

b ) Làm tương tự 

=> 2 f(x) = 6x^4 - 3x^2 - 5 + 4x^4 - 6x^3 + 7x^2 + 8x - 9

               = 10x^4 - 6x^3 + 4x^2 + 8x - 14 

=> 2.f ( x ) =  2 ( 5x^4 - 3x^3 + 2x^2 + 4x - 7 )

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

g(x) tự tìm 

ta có:

f(x) + g(x) = 6x^4 - 3x^2 - 5 

f(x) - g(x) = 4x^4 - 6x^3 + 7x^2 + 8x - 9

công hai vế lại với nhau ta được:

f(x)+g(x)+f(x)-g(x)=6x^4 - 3x^2 - 5 + 4x^4 - 6x^3 + 7x^2 + 8x - 9

=>2f(x)=6x⁴+4x⁴-6x³-3x²+7x²+8x-5-9

2f(x)=10x⁴-6x³+4x²+8x-14

2f(x)=2.(5x⁴-3x³+2x²+4x-7)

=>f(x)=5x⁴-3x³+2x²+4x-7

=>g(x)=6x^4 - 3x^2 - 5 -(5x⁴-3x³+2x²+4x-7)

=6x⁴-3x²-5-5x⁴+3x³-2x²-4x+7

=6x⁴-5x⁴+3x³-3x²-2x²-4x-5+7

=x⁴+3x³-5x²-4x+2

\(1.\)

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

\(=4x^2-2x+6x-3\)

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

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

\(2.\)

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

\(=2x^2-6x+x-3\)

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

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

\(3.\)

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

\(=3x^2+x-6x-2\)

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

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

\(4.\)

\(2x^2+5x+2\)

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

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

\(=\left(2x+1\right)\left(x+2\right)\)

\(5.\)

\(6x^2-x-1\)

\(=6x^2-3x+2x-1\)

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

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

\(6.\)

\(6x^2-6x-3\)

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

\(7.\)

\(15x^2-2x-1\)

\(=15x^2+3x-5x-1\)

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

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

\(8.\)

\(x^4-13x^2+36\)

\(=\left(x-3\right)\left(x^3+3x^2-4x-12\right)\)

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

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

Bài 1:

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

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

\(=2x-5\)

Bài 1: 

b) 

\(P\left(-1\right)=2\cdot\left(-1\right)-5=-2-5=-7\)

\(P\left(3\right)=2\cdot3-5=6-5=1\)

Bài 2: 

a) Ta có: f(x)+g(x)

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

\(=2x^2-10x+2\)

a: \(=\dfrac{6x^2+9x+8x+12}{2x+3}=\dfrac{3x\left(2x+3\right)+4\left(2x+3\right)}{2x+3}\)

=3x+4

b: \(=\dfrac{5x^2-2x+15x-6}{5x-2}\)

\(=\dfrac{x\left(5x-2\right)+3\left(5x-2\right)}{5x-2}=x+3\)

c: \(=\dfrac{-8x^2+20x+2x-5-10}{2x-5}=-4x+1+\dfrac{-10}{2x-5}\)

d: \(=\dfrac{14x^2-35x+2x-5}{2x-5}=\dfrac{7x\left(2x-5\right)+\left(2x-5\right)}{2x-5}\)

=7x+1

e: \(=\dfrac{2x^3+x^2+6x^2+3x+12x+6}{2x+1}\)

\(=\dfrac{x^2\left(2x+1\right)+3x\left(2x+1\right)+6\left(2x+1\right)}{2x+1}=x^2+3x+6\)

f: \(=\dfrac{x^3-2x^2+6x^2-12x+x-2}{x-2}=x^2+6x+1\)

g: \(=\dfrac{12x^3+6x^2-4x^2-2x+6x+3}{2x+1}=6x^2-2x+3\)