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A =(-0,1) + 0,2 + (-0,3) + 0,4 - 0,5 + 0,6 - 0,7 - (-0,8)
B = -0,1 + 0,2 - 0,3 + 0,4 - 0,5 + 0,6 - 0,7 + 0,8
B = -0,1 + ( 0,2 + 0,8) - ( 0,3 + 0,7) + ( 0,6 + 0,4) - 0,5
B = -0,1 + 1 - 1 + 1 - 0,5
B = - ( 0,1 + 0,5) + ( 1 - 1) + 1
B = -0,6 + 0 + 1
B = 0,4
\(a,x=3x^2\Rightarrow x-3x^2=0\Rightarrow x\left(1-3x\right)=0\Rightarrow\orbr{\begin{cases}x=0\\1-3x=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=0\\x=\frac{1}{3}\end{cases}}\)
\(b,\left(2x-6\right)\left(x+4\right)+2\left(2x-6\right)=0\)
\(\Rightarrow\left(2x-6\right)\left(x+4+2\right)=0\)
\(\Rightarrow\left(2x-6\right)\left(x+6\right)=0\)
\(\Rightarrow\orbr{\begin{cases}2x-6=0\\x+6=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=3\\x=-6\end{cases}}\)
\(c,\left(2x-5\right)\left(x+9\right)+6x-15=0\)
\(\Rightarrow\left(2x-5\right)\left(x+9\right)+3\left(2x-5\right)=0\)
\(\Rightarrow\left(2x-5\right)\left(x+9+3\right)=0\)
\(\Rightarrow\left(2x-5\right)\left(x+12\right)=0\)
\(\Rightarrow\orbr{\begin{cases}2x-5=0\\x+12=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{5}{2}\\x=-12\end{cases}}\)
1) \(...\Rightarrow x-7=0\Rightarrow x=7\)
2) \(...\Rightarrow x-4=0\Rightarrow x=4\)
3) \(...\Rightarrow6x-12=0\Rightarrow6x=12\Rightarrow x=12:6=2\)
4) \(...\Rightarrow9x-27=0\Rightarrow9x=27\Rightarrow x=27:9=3\)
5) \(...\Rightarrow15-x=30-25\Rightarrow15-x=5\Rightarrow x=15-5=10\)
6) \(...\Rightarrow43-24+x=20\Rightarrow19+x=20\Rightarrow x=20-19=1\)
7) \(...\Rightarrow2x+14-17=25\Rightarrow2x-3=25\Rightarrow2x=28\Rightarrow x=28:2=14\)
8) \(...\Rightarrow3x+21-15=27\Rightarrow3x-6=27\Rightarrow3x=33\Rightarrow x=33:3=11\)
9) \(...\Rightarrow15+4x-8=95\Rightarrow4x+7=95\Rightarrow4x=88\Rightarrow x=88:4=22\)
10) \(...\Rightarrow20-x-14=5\Rightarrow6-x=5\Rightarrow x=6-5=1\)
11) \(...\Rightarrow24+15-3x=27\Rightarrow39-3x=27\Rightarrow3x=39-27\Rightarrow3x=12\Rightarrow x=12:3=4\)
BS: \(x\in \mathbb{Z}\)
\(a,\Rightarrow x\in\left\{1;2;3;4\right\}\\ b,\Rightarrow x\in\left\{-3;-2;-1\right\}\\ d,\Rightarrow x\in\left\{-1;-2;-3;...\right\}\\ e,\Rightarrow x\in\left\{-4;-5;-6;...\right\}\)
a.\(x\in\left\{1;2;3;4\right\}\)
b.\(x\in\left\{-3;-2;-1\right\}\)
Bài này giống tìm nghiệm quá :
1) \(5\left(x-7\right)=0\)
\(\left(x-7\right)=0\div5\)
\(\left(x-7\right)=0\)
\(x=0+7\)
\(x=7\)
2) \(25\left(x-4\right)=0\)
\(\left(x-4\right)=0\div25\)
\(\left(x-4\right)=0\)
\(x=0+4\)
\(x=4\)
3) \(34\left(2x-6\right)=0\)
\(\left(2x-6\right)=0\div34\)
\(\left(2x-6\right)=0\)
\(2x=0+6\)
\(2x=6\)
\(x=6\div2\)
\(x=3\)
4) \(2007\left(3x-12\right)=0\)
\(\left(3x-12\right)=0\div2007\)
\(\left(3x-12\right)=0\)
\(3x=0+12\)
\(3x=12\)
\(x=12\div3\)
\(x=4\)
5) \(47\left(5x-15\right)=0\)
\(\left(5x-15\right)=0\div47\)
\(\left(5x-15\right)=0\)
\(5x=0+15\)
\(5x=15\)
\(x=15\div5\)
\(x=3\)
6) \(13\left(4x-24\right)=0\)
\(\left(4x-24\right)=0\div13\)
\(\left(4x-24\right)=0\)
\(4x=0+24\)
\(4x=24\)
\(x=24\div4\)
\(x=6\)
40 + 50 + 60 + .............. + 38540 + 38550
= 1 + 1 + 1 + .................+ 1 + 1
Từ 4 đến 3855 có số số hạng là:
( 3855 - 4 ) : 1 + 1 = 3852 ( số hạng )
\(\Rightarrow\)1 x 3852 = 3852
40+50+60+...+38540+38550
<=> 1+1+1+...+1+1
=> dãy có 3852 số hạng
<=> 1.3852
= 3852