Question 933239

what two numbers have a sum of {{{-4}}} and a difference of {{{10}}}?

let two numbers be {{{x}}} and {{{y}}}


their sum is {{{-4}}}:{{{x+y=-4}}}...eq.1

their difference is {{{-4}}}:{{{x-y=10}}}...eq.2

solve the system:

{{{x+y=-4}}}...eq.1
{{{x-y=10}}}...eq.2
________________________________add

{{{x+cross(y)+x-cross(y)=-4+10}}}

{{{2x=6}}}

{{{highlight(x=3)}}}

go to {{{x+y=-4}}}...eq.1, substitute {{{3}}} for {{{x}}} and solve for {{{y}}}

{{{3+y=-4}}}

{{{y=-4-3}}}

{{{highlight(y=-7)}}}