Jika 1 + 1/4 + 1/9 + 1/16 + 1/25 + ... = a maka, 1/9 + 1/25 + 1/49 + ... = a) - 3/4 a - 1 b) 3/2 a - 1 c) - 3/2 a + 1 d) 3/4 a + 1 e) 3/2 a tolong pakai jalan y

[tex]
1+\frac{1}{4}+\frac{1}{9}+\frac{1}{16}+\ldots=a\\
\Leftrightarrow a-1=\left(\frac{1}{4}+\frac{1}{16}+\frac{1}{36}+\ldots\right)+\left(\frac{1}{9}+\frac{1}{25}+\frac{1}{49}+\ldots\right)\\
\Leftrightarrow a-1=\frac{1}{4}\left(1+\frac{1}{4}+\frac{1}{9}+\frac{1}{16}+\frac{1}{25}+\ldots\right)+\left(\frac{1}{9}+\frac{1}{25}+\frac{1}{49}+\ldots\right)\\
\Leftrightarrow a-1=\frac{1}{4}a+\left(\frac{1}{9}+\frac{1}{25}+\frac{1}{49}+\ldots\right)\\
\Leftrightarrow a-1-\frac{1}{4}a=\frac{1}{9}+\frac{1}{25}+\frac{1}{49}+\ldots\\
\Leftrightarrow \frac{3}{4}a-1=\frac{1}{9}+\frac{1}{25}+\frac{1}{49}+\ldots
[/tex]