can't you
cancha
/ˈkæntʃə/AssimilationReduction
In real speech
What happens to the sounds
t + y blend into “ch”, and you weakens to /ə/: can't you → “CAN-cha”.
When to use it
Can't you see? Why can't you…? Often carries a note of reproach or emotion.
Casual → formal
Slang
cancha
Neutral
can't you
Formal
are you unable to
Sound notes
Assimilation: neighbouring sounds change each other, e.g. t + y → “ch”, d + y → “j”.