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a) \(2x^2-5x-12\)
\(=2x^2-8x+3x-12\)
\(=2x\left(x-4\right)+3\left(x-4\right)\)
\(=\left(x-4\right)\left(2x+3\right)\)
b) \(x^3+5x^2+8x+4\)
\(=\left(x^3+3x^2+2x\right)+\left(2x^2+6x+4\right)\)
\(=x\left(x^2+3x+2\right)+2\left(x^2+3x+2\right)\)
\(=\left(x^2+3x+2\right)\left(x+2\right)\)
\(=\left(x^2+x+2x+2\right)\left(x+2\right)\)
\(=\left[x\left(x+1\right)+2\left(x+1\right)\right]\left(x+2\right)\)
\(=\left(x+1\right)\left(x+2\right)\left(x+2\right)\)
\(=\left(x+1\right)\left(x+2\right)^2\)
c) \(x^4+x^2+1\)
\(=\left(x^4-x^3+x^2\right)+\left(x^3-x^2+x\right)+\left(x^2-x+1\right)\)
\(=x^2\left(x^2-x+1\right)+x\left(x^2-x+1\right)+\left(x^2-x+1\right)\)
\(=\left(x^2-x+1\right)\left(x^2+x+1\right)\)
\(a,\left(2x+3\right)\left(2x-3\right)-\left(2x+1\right)^2\)
\(=4x^2-9-4x^2-4x-1\)
\(=-4x-10\)
\(=-2\left(2x+5\right)\)
b,Tương tự
a,x8 +x4 +1=x6 .x2 +x3 .x+1=x6 .x2-x2 +x3 .x-x+1+x+x2=x2.(x6-1)+x.(x3-1)+1+x+x2=x2.(x3-1).(x3+1)+x.(x-1).(x2+x+1)+1+x+x2
Answer:
Câu 1:
\(\left(5x-x-\frac{1}{2}\right)2x\)
\(=\left(4x-\frac{1}{2}\right)2x\)
\(=4x.2x-\frac{1}{2}.2x\)
\(=8x^2-x\)
\(\left(x^3+4x^2+3x+12\right)\left(x+4\right)\)
\(=x\left(x^3+4x^2+3x+12\right)+4\left(x^3+4x^2+3x+12\right)\)
\(=x^4+4x^3+3x^2+12x+4x^3+16x^2+12x+48\)
\(=x^4+\left(4x^3+4x^3\right)+\left(3x^2+16x^2\right)+\left(12x+12x\right)+48\)
\(=x^4+8x^3+19x^2+24x+48\)
Ta thay \(x=99\) vào phân thức \(\frac{x^2+1}{x-1}\): \(\frac{\left(99\right)^2+1}{99-1}=\frac{9802}{98}=\frac{4901}{49}\)
Ta thay \(x=4\) vào phân thức \(\frac{x^2-x}{2\left(x-1\right)}\) : \(\frac{4^2-4}{2.\left(4-1\right)}=\frac{12}{6}=2\)
\(\left(x+y\right)^2-\left(x-y\right)^2\)
\(= (x²+2xy+y²)-(x²-2xy+y²)\)
\(= x²+2xy+y²-x²+2xy-y²\)
\(= 4xy\)
\(4x^2+4x+1=\left(2x+1\right)^2=\left(2.2+1\right)^2=25\)
Câu 2:
\(x^2+x=0\)
\(\Rightarrow x\left(x+1\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x=0\\x+1=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=0\\x=-1\end{cases}}\)
\(x^2.\left(x-1\right)+4-4x=0\)
\(\Rightarrow x^2.\left(x-1\right)+4\left(1-x\right)=0\)
\(\Rightarrow\left(x-1\right)\left(x^2-4\right)=0\)
\(\Rightarrow\left(x-1\right)\left(x-2\right)\left(x+2\right)=0\)
Trường hợp 1: \(x-1=0\Rightarrow x=1\)
Trường hợp 2: \(x-2=0\Rightarrow x=2\)
Trường hợp 3: \(x+2=0\Rightarrow x=-2\)
Câu 3: Bạn xem lại đề bài nhé.
a) \(2a^{n+2}b^n-18a^nb^{n+2}\)
\(=2a^nb^n\left(a^2-9b^2\right)\)
\(=2a^nb^n\left(a-3b\right)\left(a+3b\right)\)
\(x^3-4x^2+5x-2\)
\(=\left(x^3-x^2\right)-\left(3x^2-3x\right)+\left(2x-2\right)\)
\(=\left(x-1\right).\left(x^2-3x+2\right)\)
\(=\left(x-1\right).[\left(x^2-x\right)-\left(2x-2\right)]\)
\(=\left(x-2\right).\left(x-1\right)^2\)
\(x^5+x+1\)
\(=x^5-x^2+x+1\)
\(=x^2.\left(x^3-1\right)+\left(x^2+x+1\right)\)
\(=x^2.\left(x-1\right).\left(x^2+x+1\right)+\left(x^2+x+1\right)\)
\(=\left(x^2+x+1\right).\left(x^3-x^2+1\right)\)
\(x^3+5x^2+5x+1\)
\(=\left(x+1\right).\left(x^2-x+1\right)+5x.\left(x+1\right)\)
\(=\left(x+1\right).\left(x^2+4x+1\right)\)
\(x^2.\left(x^2+2y^2\right)-3y^4\)
\(=x^4+2x^2y^2-3y^4\)
\(=x^4+2x^2y^2+y^4-4y^4\)
\(=\left(x^2+y^2\right)-4y^4\)
\(=\left(x^2+y^2-2y^2\right).\left(x^2+y^2+2y^2\right)\)
\(=\left(x^2-y^2\right).\left(x^2+3y^2\right)\)
\(=\left(x-y\right).\left(x+y\right).\left(x^2+3y^2\right)\)