Verified answer

Sum of roots = 5 + k. Product of roots = 5k. So 5 + k = 5k, k = 5/4.

the equation is (x - 5)(x - 5/4) = 0. (x - 5)(4x - 5) = 0. 4x^2 - 25x + 25) = 0

(x-5)*(x-k)=0 [x為變數的二次方程的根是5和k]

5+k=5*k [兩根的和相等於兩根的積]

5+k=5*k

-->4*k=5

-->k=1.25

(x-5)*(x-1.25)=0

-->x^2- 6.25 x+6.25=0