Let x=number 1 let y=number2
there sum is equal to 70
then
number1+number2=70
substituting
x+y=70
y=70-x
let there product will be p
p=xy
substituting
p=x(70-x)
which is choice c
700 is what is half of that I think
The plus-minus sign represents that there are two possible outcomes.
In this case, we have

. When we branch out the possibilities we got 2 values:

and

Those are the roots of this equation. When they ask their product, they want you to multiply both numbers.
When we multiply them:

When we FOIL the we get:

Simplify:


So the product of the two roots of this equation is 6.
See https://web2.0calc.com/questions/need-help-now_10.