Question

Answer 1

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

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

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

2: Chu vi là 14x-4

=>AB+AC+BC=14x-4

=>BC+2x+3+3x+1=14x-4

=>BC+5x+4=14x-4

=>BC=14x-4-5x-4=9x-8

3: \(A=0,2\left(5x-3\right)-\dfrac{1}{2}\left(\dfrac{2}{3}x+6\right)+\dfrac{2}{3}\left(3-x\right)\)

\(=x-0,6-\dfrac{1}{3}x-3+2-\dfrac{2}{3}x\)

=-1,6

4: Đặt \(\left(x-1\right)+\left(x-2\right)+\left(x-3\right)+...+\left(x-99\right)+\left(x-100\right)=0\)

=>\(100x-5050=0\)

=>100x=5050

=>x=505/10=50,5

5:

C(x)+D(x)=\(2x^5-4,8x^3+4x+20\)

=>\(D\left(x\right)=2x^5-4.8x^3+4x+20-C\left(x\right)\)

\(=2x^5-4,8x^3+4x+20-5x^4+4,8x^3-2,5x^2+16x-25\)

\(=2x^5-2,5x^2+20x-5\)