Question

If one root of quadratic equation x2-11x +k =0 is 9.find the value of k.

Answer 1

let the other root be y
therefore two roots will be 9 and y
as the roots sum should be equal to - b/a
therefore 9 + y= -(-11)/1
therefore y = 2
and also the product of roots is equal to c/a
therefore (9)(2) = k/1
therefore k = 18

Answer 2

x^2-11x+k=0

(9)^2-11(9)+k=0. {One root of equation is 9}

81-99+k=0
k=18