(y+1)+(y+3)+............+(y+99)=0

=>y+1+y+3+...........+y+99=0

=>50y+(1+3+.........+99)=0

=>50y+2500=0

=>50y=0-2500

=>50y=-2500

=>y=-2500:50

=>y=-50

\(\left(y+1\right)+\left(Y+3\right)+...+\left(y+99\right)=2550\)
\(\left(y+y+..+y\right)+\left(1+3+5+...+99\right)\)
\(50y+\frac{\left(99+1\right).50}{2}=2550\)
\(50y+2500=2550\)
\(\Rightarrow50y=50\)
\(\Rightarrow y=50:50=1\)

\(\Rightarrow y+y+...+y+1+3+...+99=2550\Rightarrow50y+\frac{\left(99+1\right)\cdot50}{2}=2550\)

\(\Rightarrow50y+2500=2550\Rightarrow50y=50\Rightarrow y=1\)

mình chịu thôi nhưng bạn cho mình 1 điểm đi

Đề sai đáng ra 5049 là 5050 chứ

\(\left(y+1\right)+\left(y+2\right)+\left(y+3\right)+...+\left(y+99\right)=2550\)

Có \(\left(99-1\right):1+1=99\)cặp

\(\left(y+y+y+...+y\right)+\left(1+2+3+...+99\right)=2550\)

\(99y+\left[\left(99+1\right)\times99:2\right]=2550\)

\(99y+4590=2550\)

\(99y=2550-4590\)

\(99y=-2040\)

\(y=\frac{-680}{33}\)

Đề hình như sai bạn ơi

#)Giải :

\(\left(y+1\right)+\left(y+2\right)+\left(y+3\right)+...+\left(y+99\right)=2550\)

\(\Rightarrow\left(y+y+y+...+y\right)+\left(1+2+3+...+99\right)=2550\)

\(\Rightarrow99y+\frac{\left(99+1\right).99}{2}=2550\)

\(\Rightarrow99y+4950=2550\)

\(\Leftrightarrow99y=-2400\)

\(\Leftrightarrow y=-24,2424242424.................\approx-24,24\)

P/s : Có j đó sai sai :v đề lỗi ak ?

1.
\(\left(\frac{3}{1\times3}+\frac{3}{3\times5}+\frac{3}{5\times7}+...+\frac{3}{97\times99}\right)-x:\frac{3}{2}=\frac{7}{3}\\ \left(\frac{2}{1\times3}+\frac{2}{3\times5}+\frac{2}{5\times7}+...+\frac{2}{97\times99}\right):\frac{3}{2}-x:\frac{3}{2}=\frac{7}{3}\\\left[\left(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}+\frac{1}{5}-\frac{1}{7}+...+\frac{1}{97}-\frac{1}{99}\right)-x\right]:\frac{3}{2}=\frac{7}{3}\\ \left(1-\frac{1}{99}\right)-x=\frac{7}{3}\times\frac{3}{2}\\ \frac{98}{99}-x=\frac{7}{2}\\ x=\frac{98}{99}-\frac{7}{2}=\frac{-497}{198}\)

2.\(\frac{x}{y}=\frac{4}{3}\Rightarrow\hept{\begin{cases}x=4a\\y=3a\\x-y=4a-3a=a\end{cases}}\\ \left(x-y\right)^{2015}=5^{2015}\Rightarrow x-y=5\\ \Rightarrow a=5\Rightarrow\hept{\begin{cases}x=4\times5=20\\y=3\times5=15\end{cases}}\)

1.

Ta có : x = 1.2 + 2.3 + 3.4 + ... + 99.100

              = 1.(1 + 1) + 2.(2 + 1) + ... + 99.(99 + 1)

              = 1.1 + 1 + 2.2 + 2 + ... + 99.99 + 99

              = (1.1 + 2.2 + 3.3 + ... + 99.99) + (1 + 2 + 3 + ... + 99)

              = y + 99.(99 + 1) : 2

              = y + 99.50

              = y + 4950

=> x = y + 4950

=> x - y = 4950 

Vậy x - y = 4950 

bn nhân 3 vào x và y rồi l x - y là s