If the value of y varies directly with x and y=-1 when x=3, find y if x=9

1.If y varies directly with x

Introduce the constant term k

2.y=kx

where k is the constant term

substitute the value of x and y to form the law

-1=3k

k=-1\3

:y=-1\3xis the law

To find the value of y when x is 9

Reinstate the law which is y=-1\3x and substitute the value of x to find y

y=-1\3*9

y=-3

solution:

the given function is ,

      =

the three roots of this quadratic function is , 0 ,8 and 10.all the roots are real and rational.

if a quadratic equation is of the form ,

sum of the roots = a + b +c= 0+8+10=18=  

product of roots taken two at a time = a b + b c+ c a = 0+80+0=80 =  

product of roots = a b c = 0=  

there are 11 doors in a hall starting from 0 to 11.the entry in the hall is permitted through gate number 0 and exit is allowed through only gate number 8 and 10.so, three roots(0,8,10) of quadratic function is given by entry and exit route of this hall.

step-by-step explanation: 4 cause 2+2=4