trước khi bị gẫy cây cao số mét là

            1,75 + 3 = 4,75 (m)

                 đs...

Khi chưa bị gãy cây cao :

1,75 + 3 = 4,75 ( m )

 Đáp số : 4,75 m

x+75%x=-1,6

\(\Rightarrow x+\dfrac{3}{4}.x=\dfrac{-16}{10}\)

\(\Rightarrow x.\left(\dfrac{3}{4}+1\right)=\dfrac{-8}{5}\)

\(\Rightarrow x.\dfrac{7}{4}=\dfrac{-8}{5}\)\(\Rightarrow x=\dfrac{-8}{5}:\dfrac{7}{4}=\dfrac{-32}{35}\)

x+75%.x=-1,6

= x.1 + 75% . x = -1,6

= x. ( 1 + 75% ) = -1,6

= x . 7/4 = -1,6

= x = -16/10    : 7/4

= x =  -32/35 

xy + 2x = y = 3 , thay y = 3

=> 3x+2x = 3

=> 5x = 3

=> x = \(\dfrac{3}{5}\) ( vô lý )

b,ta có \(-0,76=\dfrac{-76}{100}=\dfrac{-19}{25}\)

ta biết:\(\dfrac{19}{25}>\dfrac{19}{28}\)

\(\dfrac{-19}{25}< \dfrac{-19}{28}\)

-0,76 và -19/28 

-0,76 = -19/25 ; -19/28

⇒ -19/25 < -19/28

nên -0,76 < -19/28

0,(31) = 0,3(13)

0,(31)=0,3(13)

0,31=0,3100>0,3(13)=0,3131313

\(\dfrac{5^5+3.5^4-6.5^3}{34}\) = \(\dfrac{5^3.\left(5^2+3.5-6\right)}{34}\) = \(\dfrac{5^3.\left(25+15-6\right)}{34}\) = \(\dfrac{5^3.34}{34}\) = 5³

= 125

\(\dfrac{5^3+3.5^4-6.5^3}{34}\)

\(=\dfrac{5^3.\left(1+3.5-6\right)}{2.17}\)

\(=\dfrac{125.\left(1+15-6\right)}{2.17}\)

\(=\dfrac{125.10}{2.17}\)

\(=\dfrac{125.5}{17}\)

\(=\dfrac{625}{17}\)

\(\dfrac{7^3+3.7^2}{10}\) = \(\dfrac{7^2.\left(7+3\right)}{10}\) = \(\dfrac{7^2.10}{10}\) = 7² = 49

\(\dfrac{5^5+3.5^4-6.5^3}{34}\) = \(\dfrac{5^3.\left(5^2+3.5-6\right)}{34}\) = \(\dfrac{5^3.\left(25+15-6\right)}{34}\) = \(\dfrac{5^3.34}{34}\) = 5³

= 125