Question 230704
X+Y=21 OR X=21-Y
X^2+Y^2=15^2
REPLACE THE X TERM IN THE SECOND EQUATION WITH (21-Y) & SOLVE FOR Y.
(21-Y)^2+Y^2=15^2
441-42Y+Y^2+Y^2=225
2Y^2-42Y+441-225=0
2Y^2-42Y+216=0
2(Y^2-21Y+108)=0
2(Y-12)(Y-9)=0
Y-12=0
Y=12 ANS. X=9 ANS.
Y-9=0
Y=9 ANS. X=12 ANS.
PROOF:
9^2+12^2=15^2
81+144=225
225=225