Question

y=3x+2/5-4x 求定义域和值域

Answer 1

y=(3x+2)/(5-4x)

定义域,分母不为0

∴ 5-4x≠0

即 x≠5/4

即定义域是{x|x≠5/4}

值域

y=(3x+2)/(5-4x)

=[(-3/4)(5-4x)+2+15/4]/(5-4x)

=(-3/4)+(23/4)/(5-4x)

∵ 5-4x≠0

∴ (23/4)/(5-4x)≠0

∴ (-3/4)+(23/4)/(5-4x)≠-3/4

即值域是{y|y≠-3/4}