Hello, Adward,
A quadratic equation having the form Ax^2 +Bx +c = 0 that contains roots -1 and 5 should contain the factors (x +1) and (x-5). Let's multiply those two together:
= x^2 - 4x -5
That contains the roots -1 and 5.
But we need the leading coefficient to be 3, so multiply by 3:
= 3x^2 - 12x -15
That meets all the requirements.
Bob

Robert S.
09/10/20
Jeffrey K.
I would complete this an equation, namely, 3x^2 - 12x -15 = 009/09/20