https://img851.imageshack.us/img851/...at25122011.jpg
https://img849.imageshack.us/img849/...at25122011.jpg
https://img72.imageshack.us/img72/9859/mat25122011.jpg

https://img607.imageshack.us/img607/...at25122011.gif

https://img834.imageshack.us/img834/...at25122011.gif

https://img39.imageshack.us/img39/2922/mat25122011.gif

3)2a-4a=12
a=-6
labl=8,-2
ab=2√17