Question

若

x

3

=

y

4

=

z

5

，則

x+y

x-2y+3z

=

7

10

．

Answer 1

分析：首先設(shè)

x

3

=

y

4

=

z

5

=k，則可得x=3k，y=4k，z=5k，然后代入

x+y

x-2y+3z

，再化簡(jiǎn)求解即可求得．

解答：解：設(shè)

x

3

=

y

4

=

z

5

=k，
則x=3k，y=4k，z=5k，
則

x+y

x-2y+3z

=

3k+4k

3k-8k+15k

=

7

10

．
故答案為：

7

10

．

點(diǎn)評(píng)：此題考查了比例的性質(zhì)．此題比較簡(jiǎn)單，注意掌握設(shè)

x

3

=

y

4

=

z

5

=k的解題方法是解此題的關(guān)鍵．