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Ta có :
252/x = 84/97
=> x = 252/84/97
=> x = 291
Vậy nhé, nhớ k cho mk đó
\(\left(a\right)\frac{34-x}{30}=\frac{5}{6}\)
\(\frac{34-x}{30}=\frac{25}{30}\)
34 - x = 25
x = 34 - 25 = 9
\(\left(b\right)\frac{x+13}{34}=\frac{12}{17}\)
\(\frac{x+13}{34}=\frac{24}{34}\)
x + 13 = 24
x = 24 - 13 = 11
\(\left(c\right)\left(x+\frac{1}{3}\right)+\left(x+\frac{1}{9}\right)+\left(x+\frac{1}{27}\right)+\left(x+\frac{1}{81}\right)=\frac{56}{81}\)
\(4x+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}=\frac{56}{81}\)
Đặt \(A=\frac{1}{3}+\frac{1}{9}+\frac{1}{27}+\frac{1}{81}\)
Ta có : \(3A=1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}\)
\(3A-A=1+\frac{1}{3}+\frac{1}{9}+\frac{1}{27}-\frac{1}{3}-\frac{1}{9}-\frac{1}{27}-\frac{1}{81}\)
\(2A=1-\frac{1}{81}=\frac{80}{81}\)
\(A=\frac{80}{81}\div2=\frac{40}{81}\)
\(\Rightarrow4x+\frac{40}{81}=\frac{56}{81}\)
\(4x=\frac{56}{81}-\frac{40}{81}\)
\(4x=\frac{16}{81}\)
\(x=\frac{16}{81}\div4=\frac{4}{81}\)
Theo đầu bài ta có:
\(\frac{x-7}{7}+\frac{x-7}{8}=\frac{15}{56}\)
\(\Rightarrow\left(x-7\right)\cdot\frac{1}{7}+\left(x-7\right)\cdot\frac{1}{8}=\frac{15}{56}\)
\(\Rightarrow\left(x-7\right)\cdot\left(\frac{1}{7}+\frac{1}{8}\right)=\frac{15}{56}\)
\(\Rightarrow\left(x-7\right)\cdot\frac{15}{56}=\frac{15}{56}\)
\(\Rightarrow x-7=1\)
\(\Rightarrow x=8\)
\(x+x\times\frac{1}{3}:\frac{2}{9}+x:\frac{2}{7}=252\)
\(x+x\times\frac{3}{2}+x\times\frac{7}{2}=252\)
\(x\times\left(1+\frac{3}{2}+\frac{7}{2}\right)=252\)
\(x\times6=252\)
\(x=252:6\)
\(x=42\)
X + X x \(\frac{1}{3}\)x\(\frac{9}{2}\)+ X x\(\frac{7}{2}\)= 252
X + X x \(\frac{3}{2}\)+ X x \(\frac{7}{2}\)= 252
X x (\(\frac{3}{2}\)+ \(\frac{7}{2}\)+1) = 252
X x (\(\frac{3}{2}\)+ \(\frac{7}{2}\)+ \(\frac{2}{2}\)) = 252
X x 6 = 252
X = 252 : 6
X= 42
Chúc bạn học tốt! ^^
Tim x:
x X 12 + x X 14 + x X 18 = \(\frac{21}{24}\)
x X (\(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}\)) = \(\frac{21}{24}\)
x X (\(\frac{4}{8}+\frac{2}{8}+\frac{1}{8}\)) = \(\frac{21}{24}\)
x X \(\frac{9}{8}\)= \(\frac{21}{24}\)
x = \(\frac{21}{24}\): \(\frac{9}{8}\)
x = \(\frac{21}{24}\)X \(\frac{8}{9}\)
x = \(\frac{7}{9}\)
\(x\times\frac{1}{2}+x\times\frac{1}{4}+x\times\frac{1}{8}=\frac{21}{24}\)
\(\Rightarrow x\times\left[\frac{1}{2}+\frac{1}{4}+\frac{1}{8}\right]=\frac{21}{24}\)
\(\Rightarrow x\times\left[\frac{4+2+1}{8}\right]=\frac{21}{24}\)
\(\Rightarrow x\times\frac{7}{8}=\frac{21}{24}\)
\(\Rightarrow x\times\frac{7}{8}=\frac{7}{8}\)
\(\Rightarrow x=\frac{7}{8}:\frac{7}{8}=1\)
x=291
x=21
x.84=252.97
x=24444:84
x=291
x.24=9.56
x=504:24
x=21
k nha