Question

已知3x-2y-5z=0,2x-5y+4z=0,且x,y,z均不为0,求3x*x+2y*y+5z*z/5x*x+y*y-

Answer 1

【解】

视z为常数,由已知两方程,可解得

x=3z

y=2z

将其代入待求值式中,得

3x*x+2y*y+5z*z/5x*x+y*y-9z*z

=[3(3z)^2+2(2z)^2+5z^2]/[5(3z)^2+(2z)^2-9z^2]

=40z^2/40z^2

=1