Answer:
k = -54
Explanation:
5(x^2-k/5x+8)=0
write in factor form:
(x - 4/5)(x - ?) = x^2 - k/5x + 8
expand out:
x^2 + ?x - 4/5x - 4/5(-?) = x^2 - k/5x + 8
so -4/5(-?) will be equal + 8, then
take 8/(-4/5) = -10
replace -10 with ?
x^2 + (-10)x - 4/5x - 4/5(-10)
x^2 - 54/5x + 8
mutiply by five to get the original num
5(x^2 - 54/5x + 8)
5x^2 - 54x +40
k=-54