Question

for what value of k ,x=a is a solution of equation x^2-(a+b)x +k=0​

Answer 1

x^2 - (a+b)x + k = 0

k = (a+b)x - x^2

Taking 'x' common is RHS

k = x(a+b-x)

so, k must include x and b to cancel out x and b in RHS

We asume k to be xb

xb = x(a+b-x)

cancel 'x' in both sides

b = a+b-x

b-b = a-x

0 = a-x

a = x

Therefore, k= xb