và là sao?

Hai cái này bằng nhau nha bn!

Học tốt!!!

à so sánh Bình An nói đúng rồi

3,14x\(\frac{4}{5}\)=2,512

\(2\frac{1}{2}x2x3,14=15,7\)

3,14x4/5=2,512

2/1/2x2x3,14=15,7

vl

Ta có \(\frac{9}{25}x+\frac{3}{5}.\frac{9}{25}x+\frac{3}{5}.18+\frac{9}{25}x+18=x\)

=> \(\frac{9}{25}x\left(1+\frac{3}{5}+1\right)+18\left(\frac{3}{5}+1\right)=x\)

=> \(\frac{117}{125}x+28,8=x\)

=> \(x-\frac{117}{125}x=28,8\)

=> \(\frac{8}{125}x=28,8\)

=> x = 450

Vậy x = 450

\(\frac{9}{25}x+\frac{3}{5}.\frac{9}{25}x+\frac{3}{5}.18+\frac{9}{25}x+18=x\)

\(x\left(\frac{9}{25}+\frac{9}{25}+\frac{9}{25}\right).\frac{3}{5}+\frac{3}{5}.18+18=x\)

\(x.\frac{3}{5}\left(\frac{27}{25}+18\right)+18=x\)

\(x.\frac{3}{5}\left(\frac{27}{25}+\frac{450}{25}\right)+18=x\)

\(x.\frac{3}{5}.\frac{477}{25}+18=x\)

\(x.\frac{1431}{125}+\frac{2250}{125}=x\)

\(x.\frac{3681}{125}=x\)

vậy chac tui làm sai rồi

Từ \(\frac{9-x}{7}+\frac{11-x}{9}=2\)

\(=>\frac{9-x}{7}+\frac{11-x}{9}-2=0\)

\(=>\frac{9-x}{7}+\frac{11-x}{9}-1-1=0\)

\(=>\left(\frac{9-x}{7}-1\right)+\left(\frac{11-x}{9}-1\right)=0\)

\(=>\frac{2-x}{7}+\frac{2-x}{9}=0=>\left(2-x\right).\left(\frac{1}{7}+\frac{1}{9}\right)=0\)

Vì \(\frac{1}{7}+\frac{1}{9}\) khác 0=>2-x=0=>x=2

Theo T/c dãy tỉ số=nhau:

\(\frac{x+16}{9}=\frac{y-25}{16}=\frac{z+9}{25}=\frac{x+16+y-25+z+9}{9+16+25}\)\(=\frac{\left(x+y+z\right)+\left(16-25+9\right)}{9+16+25}=\frac{x+y+z}{50}\)

Thay x=2 vào \(\frac{x+16}{9}=>\frac{2+16}{9}=\frac{x+y+z}{50}=>\frac{x+y+z}{50}=2=>x+y+z=100\)

Vậy x+y+z=100

Ta có : \(\frac{9-x}{7}=\frac{11-x}{9}=1+\frac{2-x}{7}+1+\frac{2-x}{9}=2=>\left(2-x\right)\left(\frac{1}{7}+\frac{1}{9}\right)=0=>2-x=0=>x=2\)

Thế vào tìm đc y và z rồi ra x+y+z nha bạn 

10/2 x 3,14

= 5 x 3,14

= 15,7

15,7 nha

10/2 * 3 , 14

= 5 * 3 , 14

= 15 , 7