Question

x + <x + 1> + < x + 2> + ... + 29 +30  = 30

 

Answer 1

x + <x + 1> + < x + 2> + ... + < x + 29 > + < x+30 > = 30

x + x + 1 + x + 2 + ... + x + 29 + x + 30 = 30

31x + < 1 + 2 + 3 + ... + 30 > = 30

31x + \(\frac{\left(1+30\right)\cdot\left(\left(30-1\right):1+1\right)}{2}\) = 30

31x + 465 = 30

31x = 30 - 465

31x = -435

x = -435 : 30

x = \(\frac{-435}{31}\)

Vậy x = \(\frac{-435}{31}\)

Answer 2

x + ( x + 1 ) + ( x + 2 ) + .............. + ( x + 29 ) + ( x + 30 ) = 30

\(\Rightarrow\)( x + x + x + ................... + x + x ) + ( 1 + 2 + ........... + 29 + 30 ) = 30

\(\Rightarrow\)31x + 465 = 30

\(\Rightarrow\)31x = 30 - 465 = -435

\(\Rightarrow\)x = (-435) : 31

\(\Rightarrow\)x = \(\frac{-435}{31}\)

Vậy x = \(\frac{-435}{31}\)