Question

one of the roots of equation x^2+mx-5=0 is 3 find m​

Answer 1

Answer:

${x}^{2} + mx - 5 = 0 \\ {3}^{2} + 3m - 5 = 0 \\ 9 + 3m - 5 = 0 \\ 4 + 3m = 0 \\ 3m = - 4 \\ m = \frac{ - 4}{3}$

Answer 2

Answer:

std form of a quadratic eqn : ax^2+bx+c=0

        now, lets say that the roots of the eqn : x^2+mc-5 are p andq

comparing with the std form,

  a=1, b=m and c=-5

here one of the roots is 3, so, p=3

now, we know for a quad. eqn,

sum of roots= -b/a

so here, p+q=-b/a

              3+q=-m/1 . . . . . . . (eqn1)

now, product of roots =c/a

            3q=-5/1

so, q=-5/3

replacing 'q' in eqn1,

3-5/3=-m

(9-5)/3=-m

4/3=-m

-4/3=m

ohaiyo!