1.

Which of the following sentences are statements? In case of a statement, mention whether it is true or false. (i) Paris is in France. (ii) Each prime number has exactly two factors. (iii) The equation x2 + 5|x| + 6 = 0 has no real roots. (iv) (2 + √3) is a complex number. (v) Is 6 a positive integer? (vi) The product of -3 and -2 is -6. (vii) The angles opposite the equal sides of an isosceles triangle are equal. (viii) Oh! It is too hot. (ix) Monika is a beautiful girl. (x) Every quadratic equation has at least one real root.

Answer»

(i) The sentence ‘Paris is in France’ is a statement. Paris is located in France, so the sentence given is true, so it is a statement. The statement is true.

Note: A sentence is called a mathematically acceptable statement if it is either true or false but not both. 

(ii) The sentence ‘Each prime number has exactly two factors’ is a statement. It is a mathematically proven fact that each prime number has exactly two factors, so the given sentence is true. Hence it is a statement. The statement is true. 

Note: A sentence is called a mathematically acceptable statement if it is either true or false but not both. 

(iii) The sentence ‘The equation x2 + 5|x| + 6 = 0 has no real roots.’ Is a statement. x2 + 5|x| + 6 = 0 do not have real roots. 

Case 1: (x ≥ 0) 

|x| = x: (x ≥ 0) 

x2 + 5|x| + 6 = 0 

x2 + 5x + 6 = 0 

(x + 2) (x + 3) = 0 

x = -2 and x = -3 

But we assumed x ≥ 0. So it is a contradiction. 

Case 2: (x <0) 

|x| = x: (x <0) 

x2 + 5|x| + 6 = 0 

x2 - 5x + 6 = 0 

(x - 2) (x - 3) = 0 

x = 2 and x = 3 

But we assumed x < 0. So it is a contradiction. 

So, there are no real roots for the equation x2 + 5|x| + 6 = 0 

So, the given sentence is true, and it is a statement. 

Note: A sentence is called a mathematically acceptable statement if it is either true or false but not both. 

(iv) The sentence ‘(2 + √3) is a complex number’ is a statement. 

A number which can be expressed in the form ‘a+ib’ is a complex number, (2 + √3) cannot be expressed in ‘a+ib’ form, so 2 + √3 is not a complex number. So the given sentence is a statement, and it is false. 

Note: A sentence is called a mathematically acceptable statement if it is either true or false but not both. 

(v) The sentence ‘Is 6 a positive integer?’ is a question, so it is not a statement. 

Note: A sentence which is in the form of an order, exclamation and question is not a statement. 

(vi) The sentence ‘The product of -3 and -2 is -6’ is a statement. 

Because, the product of -3 and -2 is 6 not -6, the given sentence is false. Hence the given sentence is a statement. This statement is false. 

Note: A sentence is called a mathematically acceptable statement if it is either true or false but not both. 

(vii) The sentence given is a statement. It is mathematically proven that the angles opposite to the equal sides of an isosceles triangle are equal. So the given sentence is true, and it is a statement. 

Note: A sentence is called a mathematically acceptable statement if it is either true or false but not both. 

(viii) The sentence ‘Oh! It is too hot’ is not a statement. It is an exclamation, and hot is subjective, it is not a fact, and it is an opinion. So, the given sentence is not a statement. 

Note: A sentence which is in the form of an order, exclamation and question is not a statement. 

(ix) The sentence ‘Monica is a beautiful girl’ is not a statement. The given sentence is an opinion; this can be true for some cases, false for some other case. So, the given sentence is not a statement. 

Note: A sentence is called a mathematically acceptable statement if it is either true or false but not both. 

(x) The given sentence is a statement. 

Because not every quadratic equation will have a real root. So the given sentence is false. It is a statement. This statement is false. 

Note: A sentence is called a mathematically acceptable statement if it is either true or false but not both.



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