∫a+b = 4

∴(a+b)^2=a^2+2ab+b^2= 16

ab = 3

∴a^2+b^2= 16-2×3= 10

∴(a-b)^2=a^2-2ab+b^2= 10-2ab= 10-2×3=4

∴a-b= 2

The first blank is 10 and the second blank is 2.

I hope it helps you! Hope to adopt!