x/126=-20/63

=> x=-40

x= - 40

a, => x- 1/4 = 5/12

=> x = 5/12 + 1/4

=> x = 2/3

b, => x/126 = -20/ 63

=> x/126 = -40/126

=> x = -40

a) \(5^{x+3}+5^x=126\)

\(\Rightarrow5^x\cdot\left(5^3+1\right)=126\)

\(\Rightarrow5^x\cdot\left(125+1\right)=126\)

\(\Rightarrow5^x=\dfrac{126}{126}\)

\(\Rightarrow5^x=1\)

\(\Rightarrow5^x=5^0\)

\(\Rightarrow x=0\)

b) \(\dfrac{9-3x}{2}=\dfrac{5-2x}{3}\)

\(\Rightarrow\dfrac{3\cdot\left(9-3x\right)}{6}=\dfrac{2\cdot\left(5-2x\right)}{6}\)

\(\Rightarrow3\cdot\left(9-3x\right)=2\cdot\left(5-2x\right)\)

\(\Rightarrow27-9x=10-4x\)

\(\Rightarrow-4x+9x=27-10\)

\(\Rightarrow5x=17\)

\(\Rightarrow x=\dfrac{17}{5}\)

c) \(7-4\left(x+1\right)=5\)

\(\Rightarrow4\left(x+1\right)=7-5\)

\(\Rightarrow4\left(x+1\right)=2\)

\(\Rightarrow x+1=\dfrac{1}{2}\)

\(\Rightarrow x=\dfrac{1}{2}-1\)

\(\Rightarrow x=-\dfrac{1}{2}\)

\(\dfrac{x}{126}=\dfrac{-5}{9}.\dfrac{4}{7}\)

\(\Rightarrow\dfrac{x}{126}=\dfrac{-5.4}{9.7}\)

\(\Rightarrow\dfrac{x}{126}=\dfrac{-20}{63}\); Mẫu số chung : 126

\(\)\(\Rightarrow\dfrac{x}{126}=\dfrac{-40}{126}\)

\(\Rightarrow x=-40\)

a: =11/4+5/4-9/8

=4-9/8=32/8-9/8=23/8

b: \(=\dfrac{6}{7}\cdot\dfrac{7}{4}+\dfrac{5}{3}=\dfrac{3}{2}+\dfrac{5}{3}=\dfrac{9+10}{6}=\dfrac{19}{6}\)

c: \(=\dfrac{13}{18}\cdot\dfrac{9}{5}-1=\dfrac{13}{10}-1=\dfrac{3}{10}\)

d: \(=3+\dfrac{9}{4}\cdot\dfrac{5}{3}=3+\dfrac{45}{12}=\dfrac{81}{12}=\dfrac{27}{4}\)

`a)11/4+5/4-9/8=4-9/8=32/8-9/8=23/8`

`b)6/7 xx 7/4+5/3=3/2+5/3=9/6+10/6=19/6`

`c)13/18xx9/5−1=13/10−1=3/10`

`d)3+9/4xx5/3=3+45/12=27/4`

cho hỏi tập hợp các số tự nhiên ko vượt quá 50

\(\frac{y}{126}=\frac{-5}{9}\times\frac{4}{7}\)

\(\frac{y}{126}=\frac{\left(-5\right)\times4}{9\times7}\)

\(\frac{y}{126}=\frac{-20}{63}\)

\(\frac{y}{126}=\frac{-40}{126}\)

\(\Rightarrow y=-40\)