Question

确定方程3

x2-9

+4

x2-16

+5

x2-25

=

120

x

的解集______．

Answer 1

由题意，

x2-9≥0 x2-16≥0 x2-25≥0 x＞0

，∴x≥5
∴

x2-9

≥4，

x2-16

≥3，

x2-25

≥0，
∴3

x2-9

+4

x2-16

+5

x2-25

≥24
∵3

x2-9

+4

x2-16

+5

x2-25

=

120

x

∴

120

x

≥24
∵x≥5，∴

120

x

≤24
∴

120

x

=24
∴x=5
故答案为：{5}