1.
3(х+1)+(x+1)= 3x+3+x+1=4x+4= 4(x+1)
3(y+5) -2(y-6) = 3y+15 -(2y-12)= 3y+15-2y+12=y+27
3x(x-2) -5x(x+3)= 3x²-6x-5x²-15x = -2x²-21x =- x(x-21)
2a(a-b)+2b(a+b) = 2a²-2ab+2ab+2b²= 2a²+2b² = 2(a²+b²)
2.
(3x+7)/5 = (6x+4) /5
5(3x+7)=5(6x+4)
15x+35-=30x+20
15x-30x=20-35
-15x=-15
x=1
проверим:
(3+7)/5 = (6+4)/5
10/5=10/5
2=2
(2х+1)/5 +(3х+1)/7 = 2
7(2х+1) +5(3х+1) = 2*5*7
14х+7+ 15х+5=70
29х +12=70
29х=70-12
29х=58
х=58:29
х= 2
Проверим:
(2*2+1) /5+ (3*2+1)/7 =2
5/5 + 7/7 =2
2=2
(8х-3)/7 - (3х+1)/10 =2
10(8х-3) - 7(3х+1)= 2*7*10
80х-30-(21х+7)=140
80х-30-21х-7 =140
59х-37=140
59х=140+37
59х=177
х=3
проверим:
(8*3-3)/7 - (3*3+1)/10 =2
21/7 - 10/10=2
3-1=2
2=2