4, второе
7.
(m-3)(m-2)-(m-1)(m+2)=m²-2m-3m+6-m²-2m+m+2= - 6m+8
при m= 1 1/4
- 6 *1 1/4 +8= - 7 1/2+8=1/5=0.2
8/
(2¹² *7⁸)/14⁸= (2¹² *7⁸)/(2⁸ *7⁸)=2¹²/2⁸=2⁴=2*2*2*2=4²
9.
х - (5-х)/2=(21+12х)/4
4х-2(5-х)=21+12х
4х-10+2х=21+12х
4х+2х-12х=21+10
- 6х=31
х= - 31:6
х= - 5 1/6