15x(3xX-6)=0
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\(x^6-6x^5+15x^4-20x^3+15x^2-6x+1=0\)
\(\Leftrightarrow x^6-x^5-5x^5+5x^4+10x^4-10x^3-10x^3+10x^2+5x^2-5x-x+1=0\)
\(\Leftrightarrow x^5\left(x-1\right)-5x^4\left(x-1\right)+10x^3\left(x-1\right)-10x^2\left(x-1\right)+5x\left(x-1\right)-\left(x-1\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x^5-5x^4+10x^3-10x^2+5x-1\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left[x^5-x^4-4x^4+4x^3+6x^3-6x^2-4x^2+4x+x-1\right]=0\)
\(\Leftrightarrow\left(x-1\right)\left[x^4\left(x-1\right)-4x^3\left(x-1\right)+6x^2\left(x-1\right)-4x\left(x-1\right)+x-1\right]=0\)
\(\Leftrightarrow\left(x-1\right)^2\left[x^4-4x^3+6x^2-4x+1\right]=0\)
\(\Leftrightarrow\left(x-1\right)^2\left[x^4-x^3-3x^3+3x^2+3x^2-3x-x+1\right]=0\)
\(\Leftrightarrow\left(x-1\right)^3\left[x^3-3x^2+3x-1\right]=0\)
\(\Leftrightarrow\left(x-1\right)^3\left[x^3-x^2-2x^2+2x+x-1\right]=0\)
\(\Leftrightarrow\left(x-1\right)^4\left[x^2-2x+1\right]=0\Leftrightarrow\left(x-1\right)^6=0\Leftrightarrow x=1\)
Với x > 0;x ≠ 1 ta có:
A = x + 3 x x + 1 - x - 3 x x - 1
= x + 3 x - 1 - x - 3 x + 1 x x - 1 x + 1 = x + 2 x - 3 - x - 2 x - 3 x x - 1 = 4 x x x - 1 = 4 x - 1
Vì : (3X - 18) x (X - 9) = 0
\(\Rightarrow\hept{\begin{cases}3X-18=0\\X-9=0\end{cases}\Rightarrow\hept{\begin{cases}3X=18\\X=9\end{cases}\Rightarrow}\hept{\begin{cases}X=6\\X=9\end{cases}}}\)
3 . x^3 - 12 . x = 0
3 . x^3 = 12 . x
x^3 = x . 4
x^2 = 4
x^2 = 2^2
=> x = 2
Vậy x = 2
3xX^3-12xX=0
3xXx(x^2-4)=0
Có 2 kết qủa:
x=0
x^2-4=0
x=2 hoặc x=-2
3x/4 + 3x/28 + 3x/70 + ... + 3x/304 = 18/19
=> x(3/1*4 + 3/4*7 + 3/7*10 + ... + 3/16*19) = 18/19
=> x(1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + ... + 1/16 - 1/19) = 18/19
=> x(1 - 1/19) = 18/19
=> x*18/19 = 18/19
=> x = 1
\(3.\frac{x}{4}+3.\frac{x}{28}+3.\frac{x}{70}+...+3.\frac{x}{304}=\frac{18}{19}\)
\(3.\left(\frac{x}{4}+\frac{x}{28}+\frac{x}{70}+...+\frac{x}{304}\right)\)
\(\frac{x}{4}+\frac{x}{28}+\frac{x}{70}+...+\frac{x}{304}=\frac{18}{19}:3=\frac{6}{19}\)
Nhân hai vế với 3/x ta được
\(\frac{3}{x}\left(\frac{x}{4}+\frac{x}{28}+\frac{x}{70}+...+\frac{x}{304}\right)=\frac{6}{19}.\frac{3}{x}\)
\(\frac{3}{x}.\frac{x}{4}+\frac{3}{x}.\frac{x}{28}+\frac{3}{x}.\frac{x}{70}+...+\frac{3}{x}.\frac{x}{304}=\frac{18}{19.x}\)
\(\frac{3}{4}+\frac{3}{28}+\frac{3}{70}+...+\frac{3}{304}=\frac{18}{19}:x\)
\(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{16.19}=\frac{18}{19}:x\)
\(1-\frac{1}{19}=\frac{18}{19}:x\)
\(\frac{18}{19}=\frac{18}{19}:x\)
\(x=\frac{18}{19}:\frac{18}{19}=1\)
Chúc bạn học tốt !!!
P/s: Không hiểu chỗ nào cứ ib
\(15\times\left(3x-6\right)=0\)
\(3x-6=0\div15\)
\(3x-6=0\)
\(3x=0+6\)
\(3x=6\)
\(x=6\div3\)
\(x=2\)
\(3\times x\)viết thành \(3x\)em nhé
\(15.\left(3.x-6\right)=0\)
\(3.x-6=0\)
\(3.x=6\)
\(x=6:3\)
\(x=2\)