Assume that all functions in this problem are C^inf functions on R. Let fo(x), f1(x),...fn(x) be fixed functions and define the differentiable operator L(y)= fn(x)y^n(x)+f(n-1)(x)y^(n-1)(x) +...+ f1(x)y\'(x)+fo(x)y(x) on C^inf. Verifu directly from the definition that L is linear transformation on C^inf. Please explain!!! Solution given that f0(x),f1(x),f2(x),. . . fn(x) be fixed functions and the differentiable operator L(y)=fn(x)yn(x)+fn-1(x)yn-1(x)+...+f1(x)y\'(x)+f0(x)y(x) on c^ infinity. to prove that the definition L is linear transformation we have to show that a) L(y1+y2)=L(y1)+L(y2) b) L(ay)=aL(y) now L(y1+y2)=fn(x)(y1+y2)n(x)+fn-1(x)(y1+y2)n-1(x)+ . . . +f0(x)(y1+y2)(x) =fn(x)((y1)n(x)+y2n(x))+fn-1(x)(y1n-1(x)+y2n-1(x))+ . . . +f0(x)(y1(x)+y2(x)) =(fn(x)y1n(x)+fn-1(x)y1n-1(x)+ . . . +f0(x)y1(x))+(fn(x)y2(x)+fn-1(x)y2n-1(x)+ . . . +f0y2(x)) =L(y1)+L(y2) thus L(y1+y2)=L(y1)+L(y2) (1) now we have to prove that L(ay)=aL(y) L(ay)=fn(x)(ay)n(x)+fn-1(x)(ay)n-1(x)+...+f1(x)(ay)\'(x)+f0(x)(ay)(x) =afn(x)yn(x)+afn-1(x)yn-1(x)+...+af1(x)y\'(x)+af0(x)y(x) =a(fn(x)yn(x)+fn-1(x)yn-1(x)+...+f1(x)y\'(x)+f0(x)y(x) ) =aL(y) thus L(ay)=aL(y) (2) therefore from (1) and (2) L is linear transformation on C^ infinite..