Question

solve x+y=15 and xy=36​

Answer 1

$xy = 36 - - - - (1)$

$x + y = 12 - - - - (2)$

$y = 12 - x$

put in 1

$x(12 - x) = 36$

$12x - {x}^{2} = 36$

$0 = {x}^{2} - 12x + 36$

${x}^{2} - 12x + 36 = 0$

${x}^{2} - 6x - 6x + 36 = 0$

$x(x - 6) - 6(x - 6) = 0$

$(x - 6)(x - 6) = 0$

$x = 6$

put x in equation 2

$x + y = 12$

$6 + y = 12$

$y = 12 - 6$

$y = 6$

•°• x = 6 & y = 6