how can i plot values in a parabola graph if the values are fractions. it's my first time with this things so i don't understand

plot them just like any other number. It just means you have to know how to square fractions and add them.

For instance if

f(x) = 2x^2-3x+7
f(2/3) = 2(4/9) - 3(2/3) + 7
= 8/9 - 2 + 7
= 5 8/9
= 53/9 or 5.88888