Question

Do you know the answer for the 21st one??

Answer 1

x^2+y^2=157

4x+4y=68

=>x+y=68/4

=>x+y=17

x=17-y

so in the first equation

(17-y)^2+y^2=157

289+y^2-34y+y^2=157

2y^2-34y+289-157=0

2y^2-34y+132=0

2y^2-22y-12y+132=0

2y(y-11)-12(y-11)=0

so y=6

or y=11

when

y=6

x=11

when y=11

x=6