Question

Find b and then solve the equation: 2x^2+bx−10=0, if one of its roots is 5

Answer 1

Answer:

the b value is -8, i just had this problem in my hw, and the value is -8 because the value of c will be equal to -b x a; it seems the other guy forgot the negative.

Step-by-step explanation:

Answer 2

Vietas formula tells us that the product of our two roots is equal to the constant term of a quadratic over the leading coefficient, so:

[tex] r_1r_2=-\frac{-10}{2} \implies 5*r_1=-5 \implies r_1=-1[\tex]

It also tells us that the b term in our quadratic is equal to the negative of the sum of the terms divided by the leading coefficient, so:

[tex] r_1+r_2=-\frac{b}{2} \implies 4=-\frac{b}{2} \implies b=-8 [\tex]

So, one of our roots is 5, the other is -1, and our b value is 8.