4x2+10x.
x is a common factor in both terms and both terms have an even coefficient so 2 is also a common factor.
We can combine 2 and x as 2x. Now we divide each term by 2x:
4x2/2x=(4/2)(x2/x)=2x; 10x/2x=5, so the factorisation is 2x(2x+5).
If you distribute the 2x outside the parentheses to each term within the parentheses you will get the given expression.