Question

Tìm x:

x² + (2x)² + (3x)² + (4x)² + (5x)² = 220 

x>0

Answer 1

x² + (2x)² + (3x)² + (4x)² + (5x)² = 220

<=> x² + 2².x² + 3².x² + 4².x² + 5².x² = 220

<=> x² ( 1 + 2² + 3² + 4² + 5² ) = 220

<=> x².( 1 + 4 + 9 + 16 + 25 ) = 220

<=> 55x² = 220

=> x² = 4

=> x = 2 ( vì x > 0 )

Vậy x = 2

Answer 2

=\(x^2+4x^2+9x^2+16x^2+25x^2=220\)0

\(\Rightarrow55x^2=220\Rightarrow x^2=4\Rightarrow x=\orbr{\begin{cases}2\\-2\end{cases}}\)

Answer 3

bằng 2 kết bn với mình nha