验证下列等式是否成立:①(3^3+2^3)/(3^3+1^3)=(3+2)/(3+1) (4^3+3^3)/(4^3+1

2个回答

  • ①(3^3+2^3)/(3^3+1^3)

    =[(3+2)(3²-3*2+2²)]/[(3+1)(3²-3*1+1²)]

    ={(3+2)[(3-2)²+3*2]}/{(3+1)[(3-1)²+3*1]}

    =(3+2)*7/[(3+1)*7]

    =(3+2)/(3+1)

    (4^3+3^3)/(4^3+1^3)

    =[(4+3)(4²-4*3+3²)]/[(4+1)(4²-4*1+1²)]

    ={(4+3)[(4-3)²+4*3]}/{(4+1)[(4-1)²+4*1]}

    =(4+3)*13/[(4+1)*13]

    =(4+3)/(4+1)

    经验证,等式(3^3+2^3)/(3^3+1^3)=(3+2)/(3+1)与 (4^3+3^3)/(4^3+1^3)=(4+3)/(4+1)

    均成立.

    ② 再如:(5^3+4^3)/(5^3+1^3)=(5+4)/(5+1)

    该规律可表示为:(m^3+n^3)/[m^3+(m-n)^3]=(m+n)/(m+m-n)

    ③ 原式=(100+99)/(100+1) +(99+97)/(99+2) + (98+95)/(98+3)+...+(51+1)/(51+50)

    =199/101 + 196/101 + 193/101 + ...+52/101

    =(199+196+193+...+55+52)/101

    =[(199+52)+(196+55)+(193+58)+...+(127+124)]/101

    =24*251/101

    =6024/101