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a. 12,5 - \(x\) = \(x\) + 12
\(x\) + 12 + \(x\) = 12,5
\(x\) x 1 + \(x\) x 1 = 12,5 - 12
\(x\) x (1 + 1) = 0,5
\(x\) x 2 = 0,5
\(x\) = 0,5 : 2
\(x\) = 0,25
b, 8 \(\times\) \(x\) + 3 \(\times\) \(x\) + 2 \(\times\) \(x\) = 20
\(x\) \(\times\) (8 + 3 + 2) =20
\(x\) \(\times\) 13 = 20
\(x\) = 20 : 13
\(x\) = \(\dfrac{20}{13}\)
x*12,5 -x +x *2,75=1050
x*12,5 -x*1+x*2,75=`1050
x*(12,5-1+2,75)=1050
x*14,25=1050
x=1050:14,25
x= 73,68421053
\(\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+.......+\dfrac{1}{x\cdot\left(x+1\right)}=\dfrac{122}{123}\)
\(\Leftrightarrow1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+......+\dfrac{1}{x}-\dfrac{1}{x+1}=\dfrac{122}{123}\)
\(\Leftrightarrow1-\dfrac{1}{x+1}=\dfrac{122}{123}\)
\(\Leftrightarrow\dfrac{1}{x+1}=\dfrac{1}{123}\)
\(\Leftrightarrow x=122\)
x - 40% . x = 36 30% . x + x = 52
=> x - 2/5.x = 36 => 3/10 .x + x = 52
=> x(1 - 2/5) = 36 => (3/10 + 1).x = 52
=> x. 3/5 = 36 => 13/10.x = 52
=> x = 36 : 3/5 => x = 52 : 13/10
=> x = 60 => x = 40
a) \(215+x=400\)
\(\Rightarrow x=400-215\)
\(\Rightarrow x=185\)
b) \(12,5-2x=\dfrac{1}{5}\)
\(\Rightarrow2x=12,5-\dfrac{1}{5}\)
\(\Rightarrow2x=\dfrac{123}{10}\)
\(\Rightarrow x=\dfrac{123}{10}:2\)
\(\Rightarrow x=\dfrac{123}{20}\)
15/7 x X + 6/7 x X=1575
(15/7+6/7)x X=1575
3 x X=1575
X=1575 : 3
X=525
X = 0
Y = 6
4 x X + X x Y + y
= 4 x 0 + 0 x 6 + 6
= 0 + 0 + 6
= 6
\(x\) x 12,5 x \(x\) x 10 = 36,4
=> \(x\)2 x 12,5 x 10 = 36,4
=> \(x\)2 x 125 = 36,4
=> \(x\)2 = 36,4 : 125
=> \(x\)2 = 0,2912
=> \(x\)= \(\sqrt{0,2912}\) hoặc \(-\sqrt{0,2912}\)