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Câu a trước đi ạ ^^
a) 7x - 6x2 - 2
= - 6x2 + 7x - 2
= (- 6x2 + 3x) + (4x - 2)
= 3x (- 2x + 1) + 2 (2x-1)
= - 3x ( 2x -1) + 2 (2x - 1)
= ( 2x -1 ) ( - 3x +2 )
a) \(x^2+5x+6=x^2+2x+3x+6=x\left(x+2\right)+3\left(x+2\right)=\left(x+3\right)\left(x+2\right)\)
b) \(x^2-4x+3=x^2-x-3x+3=x\left(x-1\right)-3\left(x-1\right)=\left(x-3\right)\left(x-1\right)\)
c) \(x^2+5x+4=x^2+x+4x+4=x\left(x+1\right)+4\left(x+1\right)=\left(x+4\right)\left(x+1\right)\)
d) \(x^2-x-6=x^2+2x-3x-6=x\left(x+2\right)-3\left(x+2\right)=\left(x-3\right)\left(x+2\right)\)
\(b,x^2+4x+3=x^2+3x+x+3.\)
\(=x\left(x+3\right)+\left(x+3\right)=\left(x+1\right)\left(x+3\right)\)
\(c,16x-5x^2-3=x-5x^2+15x-3\)
\(=x\left(1-5x\right)+3\left(5x-1\right)\)
\(=\left(x+3\right)\left(1-5x\right)\)
\(d,x^4+4=x^4+4x^2+4-4x^2=\left(x+2\right)^2-4x^2\)
\(=\left(x^2+2-2x\right)\left(x^2+2+2x\right)\)
a) \(\left(x-1\right)\left(x-2\right)\left(x+7\right)\left(x+8\right)+8\)
\(\Leftrightarrow[\left(x-1\right)\left(x+7\right)][\left(x-2\right)\left(x+8\right)]+8\)
\(\Leftrightarrow\left(x^2+6x-7\right)\left(x^2+6x-16\right)\)+8
Đặt \(x^2+6x-7=a\)
\(\Rightarrow a\left(a-9\right)+8\)\(\)
\(\Leftrightarrow a^2-a-8a+8\)
\(\Leftrightarrow a\left(a-1\right)-8\left(a-1\right)\)
\(\Leftrightarrow\left(a-1\right)\left(a-8\right)\)
\(\Leftrightarrow\left(x^2+6x-8\right)\left(x^2+6x-15\right)\)
Chúc bạn học tốt !!
Đề yêu cầu cái j vậy?