代入法:
由1）式：y=(5x-16)/3
代入2）式：x^2-(5x-16)^2/9=16
9x^2-25x^2+160x-256=144
16x^2-160x+400=0
x^2-10x+25=0
(x-5)^2=0
x=5
y=(5*5-16)/3=3
即只有一组解 (5,3)