Question

if x^2+1/x^2=7 find the value of x^3+1/x3 ...
ans with solving on notebook

Answer 1

${x}^{2} + \frac{1}{ {x}^{2} } = 7 \\ {x}^{2} + \frac{1}{ {x}^{2} } + 2( x)( \frac{1}{x}) = 9 \\ (x + \frac{1}{x} ) = 3 \\ {(x + \frac{1}{x}) }^{3} = 27\\ {x}^{3} + \frac{1}{ {x}^{3} } = 27 - 3 \times 3 = 18$