Question

15.
If a and B are zeros of
x2+6x-k and a?+B2=40,then k=
A)-4
B) 4
C) -2
D) 2.
(A)
(B).
(C).
D).​

Answer 1

Answer:

Step-by-step explanation:

→ f(x)=x2-6x+k

→ by comparing this eq. with ax2+bx+c = 0;

→ we get a = 1, b = -6  and c = k;

→ Suppose the roots of the equation is alpha and beta:

→ alpha + beta = -b/a

→ alpha+beta = 6/1;

→ alpha*beta = c/a;

→ alpha*beta = k

→ we know that:

→ (a+b)2 = a2+b2+2ab ;

→ Not putting the values in above eq.;

→ (6)2 = 40 + 2k;

→ 36 - 40 = 2k;

→ -4 = 2k;

→ k= -2