Question

Determine whether the function y = 3 + 2x - 7x² is increasing or decreasing at x = - 4 and x = 4

Comments

Thank you for your comment, I have added to the original answer to show the value of the derivative at x= -4 and x=4
When the derivative of the function is greater than zero, the function is increasing.  Likewise when the derivative of the function is less than zero, the function. is decreasing.
I hope this helps a bit.

Answer 1

Derivative of y = 3 + 2x - 7x²  is y' = 2 - 14x

when x = -4, derivative is 58 which is greater than zero.  Function is increasing

y'(-4) = 2 - 14(-4) = 2 + 56 = 58

when x = 4, derivative is -54 which is less than zero.  Function is decreasing

y'(4) = 2 - 14(4) = 2 - 56 = -54

Comments

How need a full explanation
From where 58 came nd -54 also