Question

find the value Of k of the product pf the roots of 2x square - 6x + k = 0 is 4.

Answer 1

The product of the roots of a polynomial in the form,ax^2+bx+c=0,can be taken as (c/a)

so in this case (k/2)=4
k=8

Answer 2

A motorist Drove 100km. if he had gone 5 km per hour faster he could
made his trip 1 hour less time. how fast did he drive?

Answer 3

You can do this one by inspection, since you know that
5*20 = 4*25 = 100

Still, to solve this kind of problem in general, follow the steps. Write what they tell you, then work for a solution:

vt = 100
(v+5)(t-1) = 100

(v+5)(100/v-1) = 100
(v+5)(100-v) = 100v
v^2+5v-500 = 0
(v-20)(v+25) = 0
v = 20