Question

If y is directly proportional to x^2 and y=18 and x=3,

(i) find the equation connecting x and y,
(ii) find the value of y when x=5,
(iii) calculate the values of x when y=32

Answer 1

Explanation:

(i)

`y=k*x^2\\\\if\ x=3, y=18 ==> 18=k*9\ ==> k=2\\\\Equation\ is:\ y=2x^2\\`

(ii)

x=5 ==> y=2*5²=50

(iii)

`32=2*x^2\\x^2=16\\x^2-4^2=0\\(x-4)(x+4)=0\\\\x=4\ or\ x=-4\\`