1 Equations, Inequalities and Sets
Sheet 1. Equations, Inequalities and Sets
Exercise 1.1. Solve the given equations.
a) (x − 3)(x + 5) = 0 b) (2 − x)(x + 3) = 0 c) x2+ 8x + 12 = 0 d) x2+ x + 1 = 0 e) x2− x − 30 = 0 f) x(x − 2) = 3(x − 2) g) (3x + 2)2 = 7(3x + 2) h) x4− 10x2+ 9 = 0 i) |2x − 5| = 3
j) 22x= 32 k) 4x− 3 · 2x− 4 = 0 l) log2x = 0 m) logx8 = 1
8 m) log2(x − 4) = 3 o) (log x)3− log x = 0 Exercise 1.2. Solve the given inequalities.
a) 4 ≤ 3x − 2 < 13 b) 2x + 1 ≤ 4x − 3 ≤ x + 7 c) |x − 5| < 2 d) |3x + 2| ≥ 4 e) x2− 5x + 6 ≥ 0 f) x2+ 2x + 1 ≤ 0 g) x3+ 3x2− 4x > 0 h) 2x < 32 i) 1
4
4x
< 1 64
j) 7x≤ 1 k) 1
3
3x−2x−3
≤ 3 l) log1
2(x + 1) > 3 m) log3(x2+ 2) > 3 n) log2(x + 1) + log2(x − 1) < 3
Exercise 1.3. For given sets A and B nd A ∪ B, A ∩ B, A \ B. Mark the results on the real axis.
a) A = {x ∈ R : x2+ 8x + 12 < 0} B = {x ∈ R : (x − 2)(x + 1) ≥ 0}
b) A =
x ∈ R : x < 1 x
B =
x ∈ R : 1 + x 1 − x > 1
c) A = {x ∈ R : 2x2+ x ≤ 1} B = {x ∈ R : |x − 1| > 2}
d) A = {x ∈ R : ||x + 1| + 2| = 2} B = {x ∈ R : x2+ x > 1}
e) A = {x ∈ R : x2 < 3} B = {x ∈ R : |x + 2| > 3}
f) A =
x ∈ R : x2− 2x x2− 4 = 0
B = {x ∈ R : |x − 1| ≤ 5}
g) A = {x ∈ R : x3+ 3x < 4x2} B = {x ∈ R : (x + 1)(x − 2)(x + 3) ≥ 0}
h) A = {x ∈ R : (2 − x)(x + 1)(x + 3) ≥ 0} B = {x ∈ R : x3− x2 ≤ 0}
i) A =
x ∈ R : 1 x < 4
B =
x ∈ R : 4 x < x
j) A =
x ∈ R : x2− 1 x2+ 1 ≥ 0
B =x ∈ R : x + 12
< 1 k) A = {x ∈ R : 2x+1 > 4} B =n
x ∈ R : 132x
< 9o
Last update: November 12, 2008 1
1 Equations, Inequalities and Sets
l) A =n
x ∈ R : 73x−5x+2 ≥√ 7o
B =n
x ∈ R : 13x+31−x
> 1o
m) A = {x ∈ R : 2x+1+ 2x−1 ≤ 20} B = {x ∈ R : 5x+ 3 · 5x−2 > 28}
n) A = {x ∈ R : 4x+1+ 22−2x < 17} B =
x ∈ R : x x + 1 > 3
o) A = {x ∈ R : log2(x2− 1) < 3} B = {y ∈ R : 0 < |y| < 3}
p) A =n
x ∈ R : log12(x + 5) > 0 o
B = {x ∈ R : log(x + 2) > 0}
q) A = x ∈ R : log√
x + 1 = 2
B =n
x ∈ R : 121−xx
≤ 1o r) A = {x ∈ R : logx(x + 1) > 1} B =
x ∈ R : 2 + x 3 − x ≤ 1
Exercise 1.4. In the Cartesian (rectangular) coordinate system mark the sets A × B and B × A, where:
a) A = [1, 5] B = [2, 3] b) A = [1, 5] B = [2, ∞] c) A = [1, 4] ∪ (5, 7) B = (1, 2]
d) A = {2} B = (1, 3) e) A = (∞, −1) B = [1, ∞) f) A = R B = {3}
g) A = R B = {3} ∪ (4, 5) h) A = {1, 2, 3} B = {4, 5}
Last update: November 12, 2008 2