Question

If 7 is the root of the quadratic equation in which a=1, b=-q and c= 21 then the value of "q" is:​

Answer 1

the general form of quadratic equation is

ax²+bx+c=0

here,

x²-qx+21=0

sunce 7 is a root, substitute x=7

7²-(7×q)+21=0

49-7q+21=0

28=7q

q=4

the equation is

x²-4x+21=0