Question

Solve...(n -1)n(n+1)=990....What is the value of n

Answer 1

Hello Friend ✌
Here is u r Ans ➡


✨
$(n - 1)n(n + 1) = 990$

✔Using This Formula ➡
$(a - b)(a + b) = a {}^{2} - b {}^{2}$

$(n {}^{2} - 1)n = 990$


$n {}^{3} - n = 990$

$n {}^{3} - n - 990 = 0$

$n {}^{3} - 100n + 99n - 990 = 0$

$n(n {}^{2} - 100) + 99(n - 10) = 0$

✔Using This Formula ➡
$(a - b)(a + b) = a {}^{2} - b {}^{2}$

$n(n - 10)(n + 10) + 99(n - 10) = 0$

$(n - 10) \times (n \times (n + 10) + 99) = 0$

$(n - 10)(n {}^{2} + 10n + 99) = 0$

$n - 10 = 0$

$n {}^{2} + 10n + 99 = 0$

$n = 10$
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