Multiply the two binomials by using the box method
(x + 2)(5x – 1) =

5x 
1 
x 
5x^{2} 
x 
2 
10x 
2 
(x + 2)(5x – 1)
= 5x^{2} – x + 10x – 2
= 5x^{2} + 9x – 2