1) -10а+3b-7/2c+1
2)-9an/2-9bn/4+5cn/32+dn/8
3)12abc+8dbc-bcm+bc/10
4)18abxy-100axy+5bxy+500xy
Х²-ху-у²=19 (7+у)²-(7+у)у-у²=19 49+14у+у²-7у-у²-у²=19
х=7+у х=7+у <span> х=7+у
</span>
у²-7у-30=0
<span>х=7+у
</span><span>у²-7у-30=0</span><span>
D=49+120=169=13</span>²
<span>у</span>₁=(7+13)/2=10<span>
у</span>₂=(7-13)/2=-3
<span>
х</span>₁=7+10=17
<span>х</span>₂=7-3=4
<span>Ответ:(17;10) и (4;-3)
</span>
16+6а+7а-7
9+13а
9+13*7,5
9+97,5
106,5
6 - 3 = 3 (к.)
Ответ: на 3 к. меньше.
8/9 :3/4+2/3=8/9 * 4/3 +2/3=32/27 + 18/27=50/27=1 23/27
8/9:(3/4+2/3)=8/9 :(9/12+8/12)=8/9 : 17/12=8/9 * 12/17=32/51
1 - 9/16 :2 1/4 - 1/12=1 - 9/16 * 4/9 - 1/12=1 - 1/4 - 1/12=9/12 -1/12=8/12=2/3
(1-9/16): 2 1/4 - 1/12=7/16 * 4/9 - 1/12=7/36 - 3/36=4/36=1/9
(1 - 9/16):(2 1/4 - 1/12)=7/16 : 2 1/6=7/16 * 6/13=21/104