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Is {X : X2 – 7x + 12 = 0} = {3, 4} ? - Mathematics

Sum

Is {x : x2 – 7x + 12 = 0} = {3, 4} ?

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Solution

x2 - 7x + 12 = 0
⇒ x2 - 4x - 3x + 12 = 0
⇒ x (x - 4) - 3(x - 4) = 0
⇒ (x - 4) (x - 3) = 0
∴ Either x - 4 = 0 
⇒ x = 4
Or
x - 3 = 0
⇒ x = 3
∴ {x : x2 - 7x + 12 = 0}
= {3, 4} is true.

Concept: Cardinal Number of a Set
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APPEARS IN

Selina Concise Mathematics Class 8 ICSE
Chapter 6 Sets
Exercise 6 (A) | Q 3.6 | Page 65
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