To compute the sum/difference of two function, simply sum/subract their expressions:
[tex] (s+t)(x) = s(x)+t(x) = (4x+4)+(x-5) = 5x-1 [/tex]
[tex] (s-t)(x) = s(x)-t(x) = (4x+4)-(x-5) = 3x+9 [/tex]
Similarly, the multiplication is defined as
[tex] (s\cdot t)(x) = s(x) \cdot t(x) = (4x+4)(x-5) [/tex]
To compute [tex](s\cdot t)(1)[/tex], substitute every occurrence of x with 1:
[tex] (s\cdot t)(1) = (4+4)(1-5) = 8\cdot (-4) = -32 [/tex]
