Question

(1X5)/x+(5X9)/x+(9X13)/x+.+2009X2013/x=503

Answer 1

你这题写错了,应该是：x/(1*5) +x/(5*9) + x/(9*13) + ...+ x/(2009*2013= 503

化简得：x( 1/(1*5) +1/(5*9) +1/(9*13) +...+ 1/(2009*2013) )=503

x( 1/4(1-1/5+1/5-1/9+1/9-1/13+...+1/2009-1/2013))=503

x(1-1/2013)/4=503

x*2012/2013=503*4

x=2013