Exercise 12.2
Solve the following inequations :
Question 1
-2≤6x-1<2Sol :
On Adding 1
-2+1≤6x-1+1<2+1
Dividing by 6
-\frac{1}{6} \leq \frac{6 x}{6}<\frac{3}{6}
-\frac{1}{6} \leq x<\frac{1}{2}
[]=\left[\frac{-1}{6}, \frac{1}{2}\right)
Question 2
-3≤4-7x<18Sol :
On subtracting 4
-3-4≤4-7x-4<18-4
-7≤-7x<14
Dividing with -7
\frac{-7}{-7} \geq \frac{-7 x}{-7}>\frac{14}{-7}
or -2<x≤1
[]=(-2,1]
Question 3
0<-\frac{x}{3}<1Sol :
Multiplying -3
0 \times(-3)>-\dfrac{x}{3} \times(-3)>1 \times(-3)
0>x>-3
or -3<x<0
[]=(-3,0)
Question 4
-7<2x-3<7Sol :
Adding 3
-7+3<2x-3+3<7+3
-4<2x<10
Dividing with 2
-\frac{4}{2}<\frac{2 x}{2}<\frac{10}{2}
-2<x<5
[]=(-2,5)
Question 7
Sol :
Multiplying by 2
-3 \times 2 \leq \frac{4-7 x}{2} \times 2 \leq 18 \times 2
-6≤4-7x≤36
Subtracting 4
-6-4≤4-7x-4≤36-4
-10≤-7x≤32
Dividing by -7
\frac{-10}{-7} \geq-\frac{7 x}{-7} \geq \frac{32}{-7}
\frac{10}{7} \geq x \geq-\frac{32}{7}
or -\frac{32}{7} \leq x \leq \frac{10}{7}
[]==\left[\frac{-32}{7}, \frac{10}{7}\right]
Question 8
Sol :
Multiplying by -5
-12 \times(-5) \geq \frac{4-3 x}{-5} \times(-5) \geq 2 \times(-5)
60-4≥4-3x-4>-10-4
56≥-32>-14
Dividing with -3
\frac{56}{-3} \leq-\frac{3 x}{-3}<\frac{-14}{-3}
-\frac{56}{3} \leq x<\frac{14}{3}
[]=\left[\frac{-56}{3}, \frac{14}{3}\right)
Question 9
Represent the solution on number line
Sol :
Subtracting 1
-\frac{1}{5}-1 \leq \frac{3 x}{10}+1-1<\frac{2}{5}-1
\frac{-1-5}{5} \leq \frac{3 x}{10}<\frac{2-5}{5}
-\frac{6}{5} \leq \frac{3 x}{10}<\frac{-3}{5}
Multiplying by \frac{10}{3}
\frac{-6}{-5} \times \frac{10}{3} \leq \frac{3 x}{10} \times \frac{10}{3}<\frac{-3}{5} \times \frac{10}{3}
-4≤x<-2
[]=[-4,-2)
Question 10
-2 \leq \frac{1}{2}-\frac{2 x}{3} \leq 1 \frac{5}{6}, x \in N
(Represent the solution set on the number line)
Sol :
Subtracting \dfrac{1}{2}
-2-\frac{1}{2} \leq \frac{1}{2}-\frac{2 x}{3}-\frac{1}{2} \leq \frac{11}{6}-\frac{1}{2}
\frac{-4-1}{2} \leq-\frac{2 x}{3} \leq \frac{11-3}{6}
-\frac{5}{2} \leq \frac{-2}{3} x \leq \frac{8}{6}
Multiplying by -\frac{3}{2}
-\frac{5}{2} \times\left(-\frac{3}{2}\right) \geq \frac{-2}{3} x \times\left(-\frac{3}{2}\right) \geq \frac{4}{3} \times\left(-\frac{3}{2}\right)
\frac{15}{4} \geq x \geq-2
or -2 \leq x \leq \frac{15}{4}
or -2 \leq x \leq 3 \frac{3}{4}, x \in N
x={1,2,3}
[]
Question 11
2x+5≤0, x-3≤0
Sol :
Subtracting 5 both sides
2x+5-5≤0-5
Dividing with 2 both sides
\frac{2x}{2} \leq-\frac{5}{2}
x \leq \frac{-5}{2}
x-3≤0
Adding both sides 3
x-3+3≤0+3
x≤3
[]
[]=\left(-\infty,-\frac{5}{2}\right]
Question 12
Sol :
x-2>0
Adding both sides 2
x-2+2>0+2
x>2
3x<18
Dividing both sides with 3
\frac{3 x}{3}<\frac{18}{3}
x<6
[]
∴ 2<x<6 , []=(2,6)
Question 15
Sol :
5x+1>-24
Subtracting both sides with 1
5x+1-1>-24-1
5x>-25
Dividing both sides with 5
\frac{5 x}{5}>-\frac{25}{5}
x>-5
5x-1<24
Adding both side with 1
5x-1+1<24+1
5x<25
Dividing both sides by 5
\frac{5 x}{5}<\frac{25}{5}
x<5
[]
Question 21
Sol :
x+2≤5
Subtracting both sides 2
x+2-2≤5-2
x≤3
3x-4>-2+x
Subtracting both side with x
3x-4-x>-2+x-x
2x-4>-2
Adding both side 4
2x-4+4>-2+4
2x>2
Dividing both side by 2
\frac{2 x}{2}>\frac{2}{2}
x>1
[]
∴1<x≤3 , []=(1.3]
Question 22
Sol :
4x+3≥2x+17
Subtracting both sides 2x
4x+3-2x≥2x+17-2x
2x+3≥17
Subtracting both sides 3
2x+3-3≥17-3
Dividing both sides with 2
\frac{2 x}{2} \geq \frac{14}{2}
x≥7
3x-5<-2
Adding both sides 5
3x-5+5<-2+5
Dividing both side by 3
\frac{3 x}{3}<\frac{3}{3}
x<1
[]
Question 23
Sol :
7x-8<4x+7
Subtracting both sides 4x
7x-8-4x<4x+7-4x
3x-8<7
Adding both sides 8
3x-8+8<7+8
3x<15
Dividing both sides by 3
\frac{3 x}{3}<\frac{15}{3}
x<5
-\frac{x}{2}>4
Multiplying both sides by -2
-\dfrac{x}{2} \times (-2)<4 x(-2)
x<-8
[]
[]=(-∞,-8)
Question 24
Sol :
3x-7>2(x-6)
3x-7>2x-12
Subtracting both sides 2x
3x-7-2x>2x-12-2x
x-7>-12
Adding both sides 7
x-7+7>-12+7
x>-5
6-x>11-2x
Adding both sides 2x
6-x+2x>11-2x+2x
6+x>11
Subtracting both sides 6
6+x-6>11-6
x>5
[]
[]=(5,∞)
Question 26
Sol :
\frac{4 x}{3}-\frac{9}{4}<x+\frac{3}{4}
Adding \frac{9}{4} both sides
\frac{4 x}{3}-\frac{9}{4}+\frac{9}{4} < x+\frac{3}{4}+\frac{9}{4}
\frac{4 x}{3}<x+\frac{3+9}{4}
\frac{4 x}{3}<x+\frac{12}{4}
Subtracting both sides with x
\frac{4 x}{3}-x<x+3-x
\frac{4 x-3 x}{3}<3
\frac{x}{3}<3
Multiplying both sides with 3
\frac{x}{3} \times 3<3 \times 3
x<9
\frac{7 x-1}{3}-\frac{7 x+2}{6}>x
\frac{2(7 x-1)-(7 x+2)}{6}>x
\frac{14 x-2-7 x-2}{6}>x
\frac{7 x-4}{6}>x
Multiplying both sides by 6
\left(\frac{7 x-4}{6}\right) \times 6>6 x
7x-4>6x
Subtracting both sides with 6x
7x-4-6x>6x-6x
x-4>0
Adding both sides 4
x-4+4>0+4
x>4
[]
[]=(4,9)
Question 27
Sol :
x≤5
-x≤5
Multiplying both sides -1
-x×(-1)≥5×(-1)
x≥-5
[]
∴-5≤x≤5
(ii) |x|>5
Sol :
x>5
-x>5
Multiplying both side -1
-x×(-1)<5×(-1)
x<-5
[]
[]=(-∞,-5)⋃(5,∞)
Question 28
Sol :
x-2≤5
Adding both sides 2
x-2+2≤5+2
x≤7
-(x-2)≤5
Multiplying both sides by -1
x-2≥-5
Adding both sides 2
x-2+2≥-5+2
x≥-3
[]
-3≤x≤7
[]=[-3,7]
(ii) |x+1|≥3
Sol :
Question 29
Sol :
A1
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