n-3r=0---(1)
nCr 乘 a to the power n-r 乘 2 to the power r = 15/4---(2)
a=? n=?
乘
請也講講當遇到這類question時~應從何入手~
更新1:
可否由(2乘a to the power 2)to the power r那裡開始解釋到最後~ 不是太明白~
更新2:
plz starting from~since 2 times a to the power 2 is even
