1.

What are the zeros of the polynomial x2-6x+k. What is the value of k of 3alpha+2beta=20.

Answer»

AnsWer :

k = -16.

Given :

  • We have expression x² -6X + k.
  • 3 alpha + 2beta = 20.

To Find :

Value of k.

Concepts Required :

\tt \blacksquare \: <klux>SUM</klux> \: of \: Zeros.  \\ \tt \alpha  +  \beta  =  \frac{ - b}{a}

\tt \blacksquare \: Product \: of \: Zeros.  \\ \tt \alpha  . \beta  =  \frac{ c}{a}

SOLUTION :

We have,

\tt \:  \: 3 \alpha  + <klux>2</klux> \beta  = 20. -  -  - (<klux>1</klux>)

Sum of zeros,

\tt \:  \:   \alpha  +  \beta  = \frac{ - b}{a}  = 6 -  -  - (2)

And,

Product of zeros,

\tt \:  \:   \alpha . \beta   =  \frac{c}{a}  = k -  -  - (3)

\rule{200}3

Now,

Taking equation (2)

\tt \implies \alpha  +  \beta  = 6

Multiply by 2, We get.

\tt \implies2 \alpha  +2  \beta  = 12. -  -  -( 4)

By equation 1 Subtracted From equation 4, We get.

\begin{tabular}{1-1} 3 \alpha + 2 \beta= 20 & \\ 2 \alpha +2 \beta = 12 & \\ \cline{1-1} \alpha = 8 & \\ \cline{1-1} \end{tabular}

\tt \implies \alpha  = 8.

Putting the value of alpha in equation 2.

\tt \implies\alpha  +  \beta  = 6.

\tt \implies8 +  \beta  = 6.

\tt \implies \beta  =  - 2.

\rule{200}3

Now, According to Question.

Putting the value of alpha and beta in equation 3, We get the value of k.

\tt \implies \alpha  \beta  = k

\tt \implies8  \times - 2 =  k.

\tt \implies  k =  - 16.

Therefore,the value of k is -16.



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