Answer:
m=-3
Step-by-step explanation:
f(1)=-(1)^2+3(1)+8=-1+3+8=10
f(5)=-(5)^2+3(5)+8=-25+15+8=-2
m_avg=(f(5)-f(1))/(5-1)=(-2-10)/(5-1)=-12/4=-3
