Question

if (x-3)is a factor of the polynomial (2x^2 + x+k) find k ..
In this ques why we put the value of x is 3 we can put value of x 4 also

Answer 1

No we cant take c as 4 because it is given that x-3 is a factor.....so everytime u hv to take that no. Only which is given as factor...

Eg...if it is given that x+5 is a factor theh u hv to take x= -5

Answer 2

well we put the value of x as 3 because it makes the polynomial zero.
see here to find the value of k
F(x) = x-3=0
x=3
so putting the value ,
f(x)=2*3^2+3+k=0
= 18+3+k = 0
at last,
K = -21.
Hence solved