1.3) m2+7m-7m-49=m2+m-49
4) 60ab-36a2+20b2-60ba=-36a2+20b2
<span>0,25(32а+24в)-3(8а+в)
8а+6в-24а-3в=-16а+3в</span>
Х+у=4 умножим на "-4"
<span>4х-5у=7
-4х-4у=-16 получим
4х-5у=7
-------------------------
-9у=-9
<u>у=1</u>
х+1=4
х=4-1=3
<u>х=3</u></span>