691 .
а)
-7х +5(2х-3) =6
-7х +10х-15 =6
3х = 6+15
3х= 21
х=21:3
х=7
-7 *7 + 5( 2*7 -3) =6
-49 +5 *11 =6
-49 +55 =6
6=6
б)
5х-7(3-х)= 2х+11
5х-21+7х=2х+11
12х -2х= 11+21
10х= 32
х= 32 :10
х=3,2
5*3,2 -7 (3-3,2) = 2*3,2 +11
16 - 7 * (-0,2) = 6,4+11
16 +1,4 = 17,4
17,4=17,4
692.
а)
2(х+5) -3(х-2) =10
2х+10 -3х +6 = 10
-х=10-16
-х=-6
х=6
2 (6+5) - 3(6-2) =10
2*11 - 3*4 = 10
22 - 12 =10
10=10
б)
2(5-х) -5 (2х-3)=1
10-2х-10х+15 =1
-12х +25=1
-12х=1-25
-12х=-24
х= (-24) : (-12)
х=2
2(5-2) -5 (2*2-3) =1
2*3 - 5*1 =1
6-5=1
1=1