Jaime T. answered 07/13/21
Duke Alum Math Tutor
The problem gives us these equations:
a + b = -5;
b^2 - 10 a = 34 (we choose a to be bigger)
The first trick we want to do is to use our first equation to solve for a:
a = -5 -b;
Next, let's plug it in to our second equation:
b^2 - 10(-5-b) = 34;
b^2 +10b + 50 = 34;
Let's complete the square so:
b^2 +10b + 25 + 25 = 34;
(b+5)^2 + 25 = 34;
(b+5)^2 = 9;
(b+5) = +3 or -3
so b = -2 or -8
If b is -2 then a must be -3 (plug into first equation: a + b = -5).
Similarly, if b is -8, a must be 3.
a = -3, b = -2 (ignore this solution since a must be bigger than b)
a = 3, b = -8
Jaime T.
Small edit: the larger number must be +3 not -3.07/13/21