#### Answer

$10x+15$

#### Work Step by Step

Subtract the area of the small square from the area of the large square to find the area of the shaded region.
Remember that the square of a binomial is the square of the first term, plus twice the product of the two terms, plus the square of the second term.
$(x+4)^2-(x-1)^2\longrightarrow$ square the binomials
=$x^2+8x+16-(x^2-2x+1)\longrightarrow$ use the distributive property to multiply by -1
=$x^2+8x+16-x^2+2x-1)\longrightarrow$ combine like terms
=$10x+15$