Answer:
(a) (-5,20) and (4,11)
Explanation:
You want the solutions to the system of equations ...
Substitution
Using the second equation to substitute for y in the firs equation, we have ...
x +x² -5 = 15
x² +x -20 = 0 . . . . . subtract 15, put in standard form
(x +5)(x -4) = 0 . . . . . factor
Zero product rule
A product is zero only when one or more factors is zero. The values of x that make the factors zero are ...
x = -5 and x = 4
The corresponding values of y are ...
y = 15 -x
y = 15 -{-5, 4} = {20, 11}
The solutions are (x, y) = (-5, 20) and (4, 11).