Question

If r1 and r2 are the roots of the quadratic equation ax^2+bx+c=0, show that r1+r2=-b/a and r1r2=c/a

Answer 1

If r1 and r2 are roots then

(x-r1)(x-r2)=0

Answer 2

x^2-x(r2)-x(r2)+(r1*r2)=x^2-x(r1+r2)+(r1^2*r2^2)

Your quadratic equation is

y=x^2-x(r1+r2)+(r1*r2)

compare to

y=ax^2+bx+c

Answer 3

a=1 , b=-(r1+r2) , and c=r1*r2

Answer 4

but a =1,

-b=-b/a=(r1+r2)
c=c/a=r1*r2

Answer 5

Thanks

Answer 6

thank you!