How do you use the limit definition to find the derivative of #y=-4x-5#? Calculus Derivatives Limit Definition of Derivative 1 Answer Steve M Oct 31, 2016 # dy/dx = -4# Explanation: By definition # f'(x) =lim_(hrarr0)( (f(x+h)-f(x))/h ) # So, with # y=-4x-5 # we have: # dy/dx = lim_(hrarr0)( ( (-4(x+h)-5) - (-4x-5) ) / h )# # :. dy/dx = lim_(hrarr0)( ( (-4x-4h-5) - (-4x-5) ) / h )# # :. dy/dx = lim_(hrarr0)( ( -4x-4h-5 +4x+5 ) / h )# # :. dy/dx = lim_(hrarr0)( -(4h) / h )# # :. dy/dx = lim_(hrarr0)( -4 )# # :. dy/dx = -4# Answer link Related questions What is the limit definition of the derivative of the function #y=f(x)# ? Ho do I use the limit definition of derivative to find #f'(x)# for #f(x)=3x^2+x# ? How do I use the limit definition of derivative to find #f'(x)# for #f(x)=sqrt(x+3)# ? How do I use the limit definition of derivative to find #f'(x)# for #f(x)=1/(1-x)# ? How do I use the limit definition of derivative to find #f'(x)# for #f(x)=x^3-2# ? How do I use the limit definition of derivative to find #f'(x)# for #f(x)=1/sqrt(x)# ? How do I use the limit definition of derivative to find #f'(x)# for #f(x)=5x-9x^2# ? How do I use the limit definition of derivative to find #f'(x)# for #f(x)=sqrt(2+6x)# ? How do I use the limit definition of derivative to find #f'(x)# for #f(x)=mx+b# ? How do I use the limit definition of derivative to find #f'(x)# for #f(x)=c# ? See all questions in Limit Definition of Derivative Impact of this question 1774 views around the world You can reuse this answer Creative Commons License