Ôn tập toán 8

DL

Tìm x : 

a) x(x - 1 ) = 0

b) 3x^2 - 6x = 0

c) x( x - 6 ) + 10( x - 6 ) = 0

d) x^3 - x = 0 

SG
15 tháng 9 2016 lúc 21:36

a) x(x - 1) = 0

=> \(\left[\begin{array}{nghiempt}x=0\\x-1=0\end{array}\right.\)=> \(\left[\begin{array}{nghiempt}x=0\\x=1\end{array}\right.\)

b) 3x2 - 6x = 0

=> 3x.(x - 2) = 0

=> x.(x - 2) = 0

=> \(\left[\begin{array}{nghiempt}x=0\\x-2=0\end{array}\right.\)=> \(\left[\begin{array}{nghiempt}x=0\\x=2\end{array}\right.\)

c) x(x - 6) + 10(x - 6) = 0

=> (x - 6)(x + 10) = 0

=> \(\left[\begin{array}{nghiempt}x-6=0\\x+10=0\end{array}\right.\)=> \(\left[\begin{array}{nghiempt}x=6\\x=-10\end{array}\right.\)

d) x3 - x = 0

=> x.(x2 - 1) = 0

=> x.(x - 1).(x + 1) = 0

=> \(\left[\begin{array}{nghiempt}x=0\\x-1=0\\x+1=0\end{array}\right.\)=> \(\left[\begin{array}{nghiempt}x=0\\x=1\\x=-1\end{array}\right.\)

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IM
15 tháng 9 2016 lúc 21:37

a) 

\(x\left(x-1\right)=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=0\\x-1=0\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x=0\\x=1\end{array}\right.\)

Vậy x=0 ; x =1

b)

\(3x^2-6x=0\)

\(\Rightarrow3x\left(x-2\right)=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=0\\x-2=0\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x=0\\x=2\end{array}\right.\)

Vậy x=0 ; x =2

c)

\(x\left(x-6\right)+10\left(x-6\right)=0\)

\(\Rightarrow\left(x-6\right)\left(x+10\right)=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}x-6=0\\x+10=0\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x=6\\x=-10\end{array}\right.\)

Vậy x=6 ; x = -10

d)

\(x^3-x=0\)

\(\Rightarrow x\left(x^2-1\right)=0\)

\(\Rightarrow x\left(x-1\right)\left(x+1\right)=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=0\\x-1=0\\x+1=0\end{array}\right.\)\(\Rightarrow\left[\begin{array}{nghiempt}x=0\\x=1\\x=-1\end{array}\right.\)

Vậy x = 0 ; x = 1 ; x= - 1

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NL
15 tháng 9 2016 lúc 21:52

a,\(x\left(x-1\right)=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=0\\x-1=0\end{array}\right.\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=0\\x=1\end{array}\right.\)

b,\(3x^2-6x=0\)

\(\Rightarrow3x\left(x-2\right)=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}3x=0\\x-2=0\end{array}\right.\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=0\\x=2\end{array}\right.\)

c,\(x\left(x-6\right)+10\left(x-6\right)=0\)

\(\Rightarrow\left(x+10\right)\left(x-6\right)=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}x-6=0\\x+10=0\end{array}\right.\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=6\\x=-10\end{array}\right.\)

d,\(x^3-x=0\)

\(\Rightarrow x^2\left(x-1\right)=0\)

\(\Rightarrow\left[\begin{array}{nghiempt}x^2=0\\x-1=0\end{array}\right.\)

\(\Rightarrow\left[\begin{array}{nghiempt}x=0\\x=1\end{array}\right.\)

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TN
15 tháng 9 2016 lúc 21:56

a) x=0 or x=1

b)3x(x-2)=0 <=>3x=0 or x-2=0 <=> x=0 or x=2

c)(x-6)(x+10)=0 <=> x-6=o or x+10=0 <=> x=6 <=>x=-10

d)x(x^2-1)=0 <=>x=0 or x^2-1=0 <=>x=0 or x=1

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