1/4a+1/8a*a^2/2 при а. =, 1,6​

1/4*8/5+1/8*8/5*(8/5)²/2

2/5+1/5* 8²/5²/2

2/5+1/5*8²/2*5²

2/5+1/5*(2³)²/2*5²

2/5+1/5*2⁶/2*5²

2/5+1/5*2⁵/5²

2/5+1/5*32/5²

2/5+32/5³

2/5+32/125

82/125