Question

If x = -a is a root of x^2 +3ax+ k =0

, then the value of K is:​

Answer 1

The given expression is p(x) = x^2+3ax+k

Root of the expression= -a

that means,

p(-a) = 0

Let's see what will we get if we put the value to it,

p( -a) = (-a)^2+ 3a(-a) + k

= a^2-3a+k

also p(-a) = 0

so,

• a^2-3a+k = 0
• a^2+k = 3a
• k = 3a-a^2

So, the value of 'k' is 3a-a^2.