Question

[Nguyễn Tuấn Tài]

Tìm x 

( \(\frac{2}{11.13}\)+  \(\frac{2}{13.15}\)+....... + \(\frac{2}{19.21}\))  462 -[  2,04 : ( x+1,5] : 0,12 = 19

Answer 1

[Lê Nguyệt Hằng]

\(\left(\frac{2}{11.13}+\frac{2}{13.15}+...+\frac{2}{19.21}\right).462-\left[2.04:\left(x+1,5\right)\right]:0,12=19\)

=> \(\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{19}-\frac{1}{21}\right).462-\left[2,04:\left(x+15\right)\right]\) \(:0,12=19\)

=> \(\left(\frac{1}{11}-\frac{1}{21}\right).462-\left[2,04:\left(x+15\right)\right]:0,12=19\) 

=> \(\frac{10}{231}.462-\left[2,04:\left(x+15\right)\right]:0,12=19\)

=>\(20-\left[2,04:\left(x+15\right)\right]:0,12=19\)

=>\(\left[2,04:\left(x+15\right)\right]:0,12=20-19=1\)

=> \(2,04:\left(x+15\right)=1.0,12=0,12\)

=> \(x+15=2,04:0,12=17\)

=> \(x=17-15=2\)

Vậy x=2

**** đi @nguyentuantai

Answer 2

[Nguyên thi mai]

Cho góc tù xOy bên trong góc xOy Vẽ tia Om và On. Sao cho goc xOm=90 Độ góc yOn bằng 90 đo

a, Chứng minh rằng góc xOn = góc yom

b, Gọi Ot là tia nằm trong góc xOy  sao cho góc xOt = góc tOy