Question

1 is the zero value of polynomial x2+kx-5 then find „k‟?

Answer 1

1 is the zero value of x2+kx-5 then x=1

x2+kx-5=0
(1)^2+k-5=0
1+k-5=0
k-4=0

k=4

Answer 2

As 1 is the zero value of polynomial :
$x {}^{2} + kx - 5$
It means that if x=1 then the polynomial equals to 0
So
$x {}^{2} + kx - 5 = 0 \: if \: x = 1\\ replacing \: x \: with \: 1 \: we \: get$
$1 {}^{2} + k \times 1 - 5 = 0$
$k - 4 = 0$
k=4
hope this helps :)