Question

当a等于1/9,b等于-3时,求下列式的值.(a+b^2)+(2a+1/1*2b^2)+...+(9a+8*9/1b^2)

急急急啊，谢了

Answer 1

你好！

数学之美团为你解答

(a+b²) + [ 2a+ b²/(1*2) ] + ……+[ 9a + b²/(8*9)]
= (a+2a+3a+……+9a) + b² [1 + 1/(1*2) + 1/(2*3) +……+1/(8*9) ]
= 45a + b² [ 1+ (1 - 1/2) + (1/2 - 1/3) +……+(1/8 - 1/9) ]
= 45a + b² [ 1+ 1 - 1/9 ]
= 45a + 17/9 b²
= 45×1/9 + 17/9 *(-3)²
= 5 + 17
= 22