Question

If and  are the zeros of the polynomial p(x) = x2
– (k + 6)x + 2(2k-1) find the value of k, if + = ½ 

Answer 1

Your answer is given below =》》》

Let α  and  β are  zeroes  of  the  polynomial  = x²  - (k  +  6)x  +  2(2k  –1).

On comparing with ax²+bx+c=0

a= 1, b= -( k+6) , c = 2(2k  –1)

Sum of zeroes (α+β)= -b/a = -(-(k+6))/1

α+β= (k+6)…………....(1)

Product of zeros(α.β)= c/a = 2(2k  –1)/1

α.β= c/a = 4k -2…………(2)

Given:  (α+β) = ½(αβ )

(k+6) = ½( 4k -2)

[From eq 1 & 2]

2 (k +6 )= 4k -2

2k +12 = 4k -2

2k -4k = -2 -12

-2k = -14

k = 14/2

k =7

Answer 2

Step-by-step explanation:

Let the roots be α,β

For a quadratic equation ax

2

+bx+c=0

Sum of roots α+β=k+6⋯(1)

Product of roots αβ=4k−2⋯(2)

According to question,

α+β=

2

αβ

From (1),(2)

⟹k+6=2k−1

⟹k=7