3. х= 7+18 = 25
4. 5х–7+х=4х–9
6х–4х=7–9
2х=–2
х=–1
5. 4а+8–(3–2а)=23
4а+8–3+2а=23
6а=23–5
6а=18
а=3
6. (2х+3)(4х–3)–17=2х(4х+1)
8х^2–6х+12х–9–17=8х^2+2х
6х–2х=26
4х=26
х=6,5
7. (х+1)/2 – (х–1)/3 = 3 |•6
3(х+1) – 2(х–1) = 18
3х+3–2х+2 = 18
х = 18–5 = 13
8. 2(х+1)^2 – (х–3)(х+3) = 7+х^2
2(х^2+2х+1) – х^2 + 9 – х^2 = 7
2х^2+4х+2–2х^2 = 7–9
4х = –2–2
4х = –4
х= –1
Они пересекутся в точке (2;1)
6*(а+1)+2*а<7*(3+a)
6*a+6+2*a<21+7*a
8*a-7*a<21-6
a<15
8а-(4в+3а)-(4а-3в)= 8а-4в-3а-4а+3в= -9а-в