Algebra question

Question

If 2x2 + 8y = 121.5 and x2 - 8y = 121.5, then x

09

0 6.36

016

07

Answer 1

x = + or - 9

y =-5.0625

add the two given equations to eliminate one variable and solve for x

3x^3 = 2(121.5) = 243

x^2 = 243/3 = 81

x = + or - sqr81

x= 9 or -9