x,y为实数,y=[√(X^2-9)+√(9-X^2)]/(X-3),则3x+4y=写出具体过程

Question

x,y为实数,y=[√(X^2-9)+√(9-X^2)]/(X-3),则3x+4y=_____
写出具体过程

Answer 1

y=[√(X^2-9)+√(9-X^2)]/(X-3)
y^=[(x^-9+2√(x^-9)(9-x^)+9-x^]/(x-3)^
y^=2√-(x^-9)^/(x-3)^
(x^-9)^≥0
x^-9=0
x^=9
x=±3
又x-3≠0
x≠3
所以x=-3
y^=0
y=0
3x+4y=3*(-3)+4*0=-9