Question

if x+y=4,xy=3,find 1/y^2+1/x^2​

Answer 1

$(x + y) = 4$

$xy = 3$

So ,

$(x + y)² = 4²$

$(x² + y²) + 2xy = 16$

$(x² + y²) + 6 = 16$

$(x² + y²) = 10$

Now ,

$\frac{1}{y²} + \frac{1}{x²}$

$=> \frac{x² + y²}{x²y²}$

$=> \frac{10}{9}$