tim x
x + 3 =6
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\(a,\dfrac{3}{8}=\dfrac{6}{x}\\ \Rightarrow x=6:\dfrac{3}{8}\\ \Rightarrow x=16\\ b,\dfrac{1}{9}=\dfrac{x}{27}\\ \Rightarrow x=\dfrac{1}{9}.27\\ \Rightarrow x=3\\ c,\dfrac{4}{x}=\dfrac{8}{6}\\ \Rightarrow x=4:\dfrac{4}{3}\\ \Rightarrow x=3\\ d,\dfrac{3}{x-5}=\dfrac{-4}{x+2}\\ \Rightarrow3\left(x+2\right)=-4\left(x-5\right)\\ \Rightarrow3x+6=-4x+20\\ \Rightarrow3x+6+4x-20=0\\ \Rightarrow7x-14=0\\ \Rightarrow7x=14\\ \Rightarrow x=2\)
a: =>6/x=3/8
hay x=16
b: =>x/27=1/9
nên x=3
c: =>4/x=4/3
nên x=3
d: =>3/x-5=-4/x+2
=>3x+2=-4x+20
=>7x=18
hay x=18/7
Ta có: \(x\left(x+1\right)\left(x+6\right)-x^3=5x\)
<=> \(\left(x^2+x\right)\left(x+6\right)-x^3=5x\)
<=> \(x^3+7x^2+6x-x^3=5x\)
<=> \(7x^2+x=0\)
<=> \(x\left(7x+1\right)=0\)
<=> \(\left[\begin{array}{nghiempt}x=0\\7x+1=0\end{array}\right.\)<=>\(\left[\begin{array}{nghiempt}x=0\\x=-\frac{1}{7}\end{array}\right.\)
Vậy x\(\in\left\{-\frac{1}{7};0\right\}\)
\(x\left(x+1\right)\left(x+6\right)=\left(x^2+x\right)\left(x+6\right)=x^3+6x^2+x^2+6x=x^3+7x^2+6x\)
Do đó \(x\left(x+1\right)\left(x+6\right)-x^3=\left(x^3+7x^2+6x\right)-x^3=7x^2+6x\)
\(\Rightarrow7x^2+6x=5x\Rightarrow7x^2=-x\Rightarrow7=\frac{-x}{x^2}=\frac{-x}{\left(-x\right).\left(-x\right)}=\frac{1}{-x}\)
\(\Rightarrow-x=\frac{1}{7}\Rightarrow x=-\frac{1}{7}\)
\(3\left(x-5\right)-2\left(2x-3\right)+3\left(6-x\right)=17\)
\(\Rightarrow3x-15-4x+6+18-3x=17\)
\(\Rightarrow-4x=8\)
\(\Rightarrow x=-2\)
Vậy x = -2
x(x+1)(x+6)-x^3=5x
(x^2+x)(x+6)-x^3=5x
x^3+6x^2+x^2+6x-x^3-5x=0
7x^2+x=0
x(7x+1)=0
x=0 hoặc 7x+1=0<=> x=-1/7
x = 6 - 3 = 3
X+3=6
X=6-3
X=3