the product of four consecutive natural numbers is 840 find the numbers (with a quadratic equation)
Answers
Answer:
The 4 consecutive numbers are 4, 5, 6, 7.
Step-by-step explanation:
Let the first number be x
Then, the second will be x + 1
The third will be x + 2
The forth will be x +3
Now, According to the question the sum of the 4 consecutive number is 840.
So,
x × (x + 1) × (x + 2) × (x + 3) = 840
⇒ [(x² + 3x + 1) −1) × (x² + 3x + 1) +1] = 840
⇒ (x² + 3x + 1)² −1 = 840
⇒ (x² + 3x + 1)² = 841
⇒ (x² + 3x + 1)² = 29²
⇒ (x² + 3x + 1) = 29
⇒ x² + 3x + 1 –29 = 0
⇒ x² + 3x - 28 = 0
⇒ (x + 7) (x - 4) = 0
⇒ x = -7 and x = 4
Taking x as -7 is not possible because -7 does not belongs to the natural number.
∴ x = 4
Now, taking value of x as 4 we get :
x = 4 ; x + 1 = 5 ; x + 2 = 6 ; x + 3 = 7
∴ The 4 consecutive numbers are 4, 5, 6, 7.
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