According to lagrange′s theorem a continuos function will have it′s derivate function will also be continuous.so for continuity of f(x)f(0)=3=af(1)=−1+3+3=m+bm+b=5and it′s derivative function should also be continuous.f(x)=−2x+3 0<x<1 =m 1<x<2f′(1)=−2+3=mm=1so b=4m(a+b)=1.(3+4)=7