both values of x are other solution?

Question

by putting x=3 in equation x^2+kx+15=0 ,ve get k=-8

nov to find other solution ve

put k=8 in above equation ,so ve get to values x=3 and x=5

my question is that hov ve come to kno that the other solution is 3 or 5?

Answer 1

put k=8 in above equation ,so ve get to values x=3 and x=5

 

if you do what you said, your equation is x²+8x+15 = 0 and one would solve it by factoring:

(x+3)(x+5) = 0 and then the solutions are x= -3 or -5.

 

Any quadratic equation has two solutions, which (on a good day) can be found by factoring--otherwise you use the quadratic formula. The usual observation that solutions might be a complex conjugate pair, or there might be a double solution  (when discriminant = 0) apply. 

 

YOU SOLVE A QUADRATIC EQUATION WHEN THE a,b,c values of it are known (ax²+bx+c=0)