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45 + x3 - 5x2 - 9x
= (x3 - 5x2) - (9x - 45)
= x2(x - 5) - 9(x - 5)
= (x - 5)(x2 - 9)
= (x - 5)(x - 3)(x + 3)
TL:
\(45+x^3-5x^2-9x\)
\(=x^2\left(x-5\right)-9\left(x-5\right)\)
\(=\left(x+3\right)\left(x-3\right)\left(x-5\right)\)
x4+2011x2+2010x+2011
=(x4+x3+x2)+(2011x2+2011x+2011)-(x3+x2+x)
=x2(x2+x+1)+2011(x2+x+1)-x(x2+x+1)
=(x2+x+1)(x2+2011-x)
x4+2011x2+2010x+2011=x4-x+2011x2+2011x+2011
=x(x3-1)+2011(x2+x+1)
=x(x- 1)(x2+x+1)+2011(x2+x+1)
=(x2+x+1)[x(x-1)+2011]
=(x2+x+1)(x2-x+2011)
1) \(\left(3x+7\right)^2-\left(2x-3\right)^2=0\)
\(\Leftrightarrow\left(3x+7-2x+3\right)\left(3x+7+2x-3\right)=0\)
\(\Leftrightarrow\left(x+10\right)\left(5x+4\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x+10=0\\5x+4=0\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=-10\\x=\frac{-4}{5}\end{cases}}\)
Vạy ...
phần 2 tương tự áp dụng \(a^2-b^2=\left(a-b\right)\left(a+b\right)\)
\((4x-1)^2-(5-3x)^2=0\)
\(\Leftrightarrow(4x-1-5-3x)(4x+1+5-3x)=0\)
\(\Leftrightarrow(x-6)(x+6)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x-6=0\\x+6=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=6\\x=-6\end{cases}}\)
Vậy : ...
a) \(x^5+x+1\)
\(=\left(x^5+x^4+x^3\right)-\left(x^4+x^3+x^2\right)+\left(x^2+x+1\right)\)
\(=x^3\left(x^2+x+1\right)-x^2\left(x^2+x+1\right)+\left(x^2+x+1\right)\)
\(=\left(x^3-x^2+1\right)\left(x^2+x+1\right)\)
b) \(6x^2-13x+6\)
\(=\left(6x^2-9x\right)-\left(4x-6\right)\)
\(=3x\left(2x-3\right)-2\left(2x-3\right)\)
\(=\left(2x-3\right)\left(3x-2\right)\)
\(x^2-10x+25\)
\(=x^2-2\cdot x\cdot5+5^2\)
\(=\left(x-5\right)^2\)
x^2 - 10x + 25
= x^2 - 5x - 5x + 5^2
= x(x - 5) - 5(x - 5)
= (x - 5)(x - 5)
\(14x^2+ 33x-5=14x^2-2x+35x-5=2x\left(7x-1\right)+5\left(7x-1\right)=\left(7x-1\right)\left(2x+5\right)\)