Question

V varies partly as the square of Q.when V 34,Q 2,and when V 190,Q 5.find V when Q 10.

Answer 1

I'm guessing you meant
v = a + bq^2
and then you provide two points:
a+4b = 34
a+25b = 190
Solve to find a and b, and then find v(10) = a+100b

Answer 2

V = kQ^2 + C , where k and C are constants

case1, V = 34, Q = 2 (you have a typo in that data, no equal sign)
34 = 4k + C
case2, V = 190, Q = 5
190 = 25k + C
subtract them:
156 = 21k
k = 52/7
from 34 = 4k + C, C = 30/7

V = (52Q^2 + 30)/7

so when Q = 10
V = (52*100+30)/7 = appr 747.14