tìm x :
28 : x + 12 : x = 5
tính nhanh nha
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tính
28.112-28.12+31
=28.(112-12)+31
=28.100+31
=2800+31
=2831
tim x
42 + 2(x-7) =128
2(x-7)=86
x-7=43
x=50
20,13 x 28 + 40,26 x 12 + 80,5 x 12
= 46,97 x 12 + 40,26 + 80,5 x 12
= 12 x ( 46,97 + 40,26 + 80,5)
= 12 x 167,73
= 2 012,76
\(\dfrac{2}{3}\times\dfrac{3}{4}+\dfrac{3}{4}\times\dfrac{2}{5}=\dfrac{3}{4}\times\left(\dfrac{2}{3}+\dfrac{2}{5}\right)=\dfrac{3}{4}\times\dfrac{16}{15}=\dfrac{4}{5}\)
\(\frac{x-28-124}{2011}+\frac{x-124-2011}{28}+\frac{x-2011-28}{124}\)\(=3\)
\(\Leftrightarrow\frac{x-152}{2011}+\frac{x-2135}{28}+\frac{x-2039}{124}=3\)\(\Leftrightarrow\left(\frac{x-152}{2011}-1\right)+\left(\frac{x-2135}{28}-1\right)+\left(\frac{x-2039}{124}-1\right)=3-1-1-1\)
\(\Leftrightarrow\frac{x-2163}{2011}+\frac{x-2163}{28}+\frac{x-2163}{124}=0\)
\(\Leftrightarrow\left(x-2163\right)\left(\frac{1}{2011}+\frac{1}{28}+\frac{1}{124}\right)=0\)
Vì \(\left(\frac{1}{2011}+\frac{1}{28}+\frac{1}{124}\right)>0\)
\(\Rightarrow x-2163=0\)
\(\Leftrightarrow x=2163\)
Vậy \(x=2163\)
Ta có:
( x + 1 ) + ( x + 4 ) + ( x + 7 ) +......+ ( x + 28 ) = 155
=> x + 1 + x + 4 + x + 7 + ...... + x + 28 = 155
=> ( x + x + x +....+ x ) + ( 1 + 4 + 7 +.....+ 28 ) = 155
=> 10x + 145 = 155
=> x = ( 155 - 145 ) : 10
=> x = 1
x . 6/5 + x : 5/42 + x + x : 5/3 = 28
x. 6/5 + x . 42/5 + x + x . 3/5 = 28
x . ( 6/5 + 42/5 + 1 + 3/5 )=28
x . 56/5 = 28
x = 28 : 56/5
x = 5/2
\(12-x\left(x-7\right)=31-3\left(x+12\right)\)
\(\Leftrightarrow12-x^2+7x=31-3x-36\)
\(\Leftrightarrow12-x^2+7x=-5-3x\)
\(\Leftrightarrow17-x^2+10x=0\)
phương trình bậc 2 lớp 8 mới học :
a)
\(26+|x|=34\)
\(\Rightarrow|x|=34-26\)
\(\Rightarrow|x|=8\)
\(\Rightarrow\orbr{\begin{cases}x=8\\x=-8\end{cases}}\)
Vậy x = 8 hoặc x = -8
(28+12):x=5
40:x=5
x=40:5
x=8
theo mik thì x=8 nhoaaa