Răspuns:
2) a) 21-20:(2*3-1)=21-20:(6-1) =21-20:5 =21-4 =17
b) 36:(25-7)+2*[17-3:(2-1) =36:18 +2*(17-3:1) =2+2*(17-3) =2+2*14=2+28=30
c) (100-25:5):5-1 =(100-5):5-1 =95:5-1 =19-1 =18
d) 120:[100-(4*15+4*5)] =120:[100-(60+20)] =120: (100-80) =120:20 =6
3) a) 2x-1 =7
2x=7+1
2x=8
x=8:2
x=4
b) 3x+2=2x+6
3x-2x=6-2
x=4
c) 2(x+1)=x+3
2x+2=x+3
2x-x=3-2
x=1
d) (2x+1):3 =5
2x+1=5*3
2x+1=15
2x=14
x=7
e) 6:(x+1) =2
x+1 =6:2
x+1=3
x=2
4)
a) 3x-1 ≤8
3x≤8+1
3x≤9
x≤3
x∈{0;1;2;3}
b) x+12 >2x+3
12-3>2x-x
9>x
x<9
x∈{0;1;2;3;4;5;6;7;8}
c) 4(2x+1)≤6x+10
8x+4≤6x+10
8x-6x≤10-4
2x≤6
x≤3 ⇒x∈{0;1;2;3}
d) 2(x-1)<x+1
2x-2<x+1
2x-x<1+2
x<3 ⇒x∈{0;1;2}
e) 3-2x>1-x
3-1>1+2x-x
2>1+x
2-1>x
1>x
x<1 ⇒x∈{0)
Explicație pas cu pas:
*-inseamna inmultire
