Question

if the sum of zeros of quadratic polynomial 3x²-kx+6is 3 find the value of k
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Answer 1

Given

sum of the quadratic equation 3x²-kx+6 is 3

To Find

we have to find the value of k

$\sf\huge\bold{\underline{\underline{{Solution}}}}$

We have quadratic equation: 3x²-kx+6

sum of zeroes = -b/a

a= 3 ,b= -k & c= 6

Sum of zeroes= -(-k/3)

Now,we have given sum of zeroes is 3

So, equate with the given value

=>sum of zeroes =3

=>-(-k/3)=3

=>k/3=3

=>k=3×3

=>k=9

Check:

=>3x²-kx+6

=>3x²-9x+6

=>x²-3x+2=0

=>x²-2x-x+2=0

=>x(x-2)-1(x-2)=0

=>(x-1)(x-2)=0

=>x=1,2

we have x= 1,2 and k =9

If the quadratic equation will be zero after putting X's value and k then it will be verified and hence ,k's value is correct.

=>3x²-kx+6

=>3(1)²-9(1)+6

=>3-9+6

=>-6+6=0

Or at x= 2

=>3(2)²-9(2)+6

=>12-18+6

=>-6+6=0

Verified✓