please help
Determine the solution set of the system.
x^2 + y^2 = 49
x + y = 7

Question

please help 
Determine the solution set of the system. 
x^2 + y^2 = 49 
x + y = 7

hoblos · Answer

solve the second equation for y
replace the result in the first equation 
you will have a quadratic equation
do you know how to solve quadratic equations ?

anonymous · Answer

nevermind. can u just tell me how did they get ''-14'' from this? 
x^2+(7-x)^2=49
x^2+49-14x+x^2=49

phi · Answer

first add -49 to both sides. what do you get ?

solomonzelman · Answer

circle and a line ;)

hoblos · Answer

(a-b)^2 = a^2 -2ab + b^2
so  (7-x)^2 = 49-14x+x^2

anonymous · Answer

yeah...but how did u get -14x

phi · Answer

hoblos showed you. FOIL http://www.khanacademy.org/math/algebra/multiplying-factoring-expression/multiplying-binomials/v/multiplying-binomials

hoblos · Answer

follow the formula
(a-b)^2 = a^2 -2ab + b^2

(7-x)^2 = 7^2 -2(7)(x) + x^2 = 49-14x+x^2

anonymous · Answer

ohh okay thanks guys:)

hoblos · Answer

any time :)