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=(x+y)^2-4(x+y)+1=3^2-4.3+1=9-12+1=-2

a) Ta có : \(A=x^2+2xy+y^2-4x-4y+1\)

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

Đến đây tự làm nha , mik chỉ hưỡng dẫn hướng làm thôi chứ ko giải ra hết cho bạn chép đâu nha, đến đây tự thế vào là ra . Tự túc là hạnh phúc  :)

Hok tốt . Nhìn câu b mik nản quá nên thôi :)

Đề phần 1 sai?

x+1 hay x-1

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

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

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

\(\Rightarrow3x^2-3x=0\)

\(\Rightarrow3x\left(x-1\right)=0\Leftrightarrow\orbr{\begin{cases}x=0\\x=1\end{cases}}\)

\(\frac{1}{-2}.\frac{1}{3}+\frac{1}{-3}.\frac{1}{4}+...+\frac{1}{-9}.\frac{1}{10}\)

\(=\frac{-1}{2.3}+\frac{-1}{3.4}+...+\frac{-1}{9.10}\)

\(=-1\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+..+\frac{1}{9}-\frac{1}{10}\right)\)

\(=-1\left(\frac{1}{2}-\frac{1}{10}\right)\)

\(=-1.\frac{4}{10}=\frac{-2}{5}\)

9979.006009

are you going to kill us?

(4568 + 3759) - (4563 + 3759)

= 4568 + 3759 - 4563 - 3759

= 3

Làm lại 

(4568 + 3759) - (4568 + 3759)

= 4568 + 3759 - 4563 + 3759

= 5

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

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

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

\(=\left(5x-1\right)\left(1-2\left(125x^3+300x^2+240x+64\right)\right)\)

\(=\left(5x-1\right)\left(1-250x^3-600x^2-480x-128\right)\)

\(=5x-1250x^4-3000x^3-2400x^2-640x-1+250x^3+600x^2+480x+128\)

\(=-1250x^4-2750x^3-1800x^2-110x+127\)

(Số hơi to)

\(B=\left(x-y\right)^3+\left(y+x\right)^3+\left(y-x\right)^3-3xy\left(x+y\right)\)

\(B=\left(x-y\right)^3+\left(y+x\right)^3-\left(x-y\right)^3-3xy\left(x+y\right)\)

\(B=\left(y+x\right)^3-3xy\left(x+y\right)\)

\(B=\left(x+y\right)\left[\left(x+y\right)^2-3xy\right]\)

\(B=\left(x+y\right)\left[x^2+2xy+y^2-3xy\right]\)

\(B=\left(x+y\right)\left(x^2-xy+y^2\right)\)

\(=x^3+y^3\)

\(2\times x+4\times x=8\)

\(\Rightarrow x\left(2+4\right)=8\)

\(\Rightarrow x.6=8\)

\(\Rightarrow x=\frac{8}{6}=\frac{4}{3}\)

2*x+ 4*x = 8

=>6*x = 8

=>x = 8:6 = 4/3

Bị thừa cái -6x nhé

bài 1: 

2(x^2-9).4(x^2-1)

=(2x^2-18)(4x^2-4)

=8x^4-8x^2-72x^2+72

=8x^4-80x^2+72

\(Bai1:2\left(x-3\right)\left(x+3\right)+4\left(x-1\right)\left(x+1\right)\)

\(=2\left(x^2-9\right)+4\left(x^2-1\right)\)

\(=2x^2-18+4x^2-4\)

\(=6x^2-22\)

\(Bai2:-\left(6x-1\right)\left(3-2x\right)+\left(3x-2\right)\left(4x-3\right)=17\)

\(\Leftrightarrow-\left(18x-12x^2-3+2x\right)+12x^2-9x-8x+6=17\)

\(\Leftrightarrow-18x+12x^2+3-2x+12x^2-9x-8x+6=17\)

\(\Leftrightarrow24x^2-37x+9-17=0\)

\(\Leftrightarrow24x^2-37x-8=0\)

Đề sai??