The original number is 7 i think.
10(x^2) = 70x
10x^2 - 70x = 0
x^2 -7x =0
Δ= b^2 -4ac
where c doesnt exist=0
Δ= 49
-b ± √Δ /2a
7 ± √49 /2
7±7/2
x is either 14/2= 7
or 1/2, which doesnt work.
Lets see:
10(7^2) = 70•7
10•49 = 490
and that is right.
i hope my logic is correct.