Question

if four time a whole number is subtracted from 3 time the square of the number the result is 15. find the number

Answer 1

Answer :-

• That number is 3 or -5/3.

Given :-

• Four times a whole number is subtracted from 3 times the square of the number the result is 15.

To Find :-

• That number.

Solution :-

Let

• That number be x
• Four times the number = 4x
• three times the square of the number = 3x²

Equation :- 3x² - 4x = 15

According to question :-

⇒ 3x² - 4x = 15

⇒ 3x² - 4x - 15 = 0

⇒ 3x² - 9x + 5x - 15 = 0

⇒ 3x (x - 3) + 5 (x - 3) = 0

⇒ (3x + 5) (x - 3) = 0

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→ 3x + 5 = 0

⇒ 3x = 0 - 5

⇒ 3x = -5

⇒ x = -5/3

→ x - 3 = 0

⇒ x = 0 + 3

⇒ x = 3

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Hence, that number is 3 or -5/3.

Answer 2

Answer :

• The number is 3

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Given :

• The number mentioned here is a whole number

• Four time a whole number is subtracted from 3 time the square of the number the result is 15

To Find :

• The number

Solution :

• Let the number be x

• According to the question :

→ 3x² - 4x = 15

→ 3x² - 4x - 15 = 0

→ 3x² - 9x + 5x - 15 = 0

→ 3x( x - 3 ) + 5( x - 3 ) = 0

→ ( x - 3 )( 3x + 5 ) = 0

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• Now ,

→ x - 3 = 0

→ x = 3

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→ 3x + 5 = 0

→ 3x = - 5

→ x = $\bold{\bf \dfrac{-5}{3}}$

• Since , it was a whole number , the number cannot be negative as whole number starts from 0 , therefore , the number is 3 .

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