7-14  ʹsubs滻ֵ
⣺Enterȷϡ
>> syms x y
>> f = x^2*y + 3*x*sqrt(y)
 f =
 x^2*y+3*x*y^(1/2)
>> subs(f, x, 5)
 ans =
 25*y+15*y^(1/2)
>> subs(f, y, 5)
 ans =
 5*x^2+3*x*5^(1/2)
>>
