There are four mobile phones in in house at 5: 00 a. m. all the for mobiles phone will ring together thereafter the first onerings very 15 minutes the second one rings every 20 minutes that one rings every 25 minutes fourth one rings every 30 minutes at what time will the for mobile phones ring together again

after 300 min that mean at they will ring at 10:00 a.m

Step-by-step explanation:

1.phone will ring after 15,30,45,60,75,90,105,120,135,150,165,180,195,210,225,240,255,270,285,300

2.phone will ring after 20,40,60,80,100,120,140,160,180,200,220,240,260,280,300

3.phone will ring after 25,50,75,100,125,150,175,200,225,250,275,300

4.phone will ring after 30,60,90,120,150,180,210,240,270,300

if the eqn of the parabola is f(x) = (x-4)(x+2), we need to mult. this out to find the coordinates of the vertex.

then f(x) = x^2 + 2x - 4x - 8, and f(x) = x^2 - 2x - 8.

one way in which you can find the vertex is to calculate x = -b / (2a).   here, that comes to

        )

x = = 1.   f(1) = 1^2 - 2(1) - 8 = - 9.   vertex is at (1, -9).

        2(1) 

find another point on the curve:   let x=0, for which y=-8.   then (0, -8) is on the curve.   plot the vertex and this point and draw a smooth parabola thru both.

hope this