Someone do this plz.

11 ) x^3 - x^2 + 6x + 7,

12 ) 3x^3 + 7x^2 - 1,

13 ) 2x^2 + 13xy - 4y^2,

14 ) - x^4 + 4x^3 - 3x,

15 ) - 5x^2 - 7xy + 6y^2,

16 ) x^2y + 5xy^2,

17 ) x = 324,

18 ) 8 / 11,

19 )  Length of missing side is 20 meters

Step-by-step explanation:

11 ) ( x^3 + 2x^2 + 5x ) - ( 3x^2 - x - 7 ) ⇒ Remove the ( ) through distribution,

x^3 + 2x^2 + 5x  -  3x^2 + x + 7 ⇒ Group like terms,

Solution; x^3 - x^2 + 6x + 7

12 ) ( x^4 + 8x^2 - 1 ) - ( x^2 - 3x^3 + x^4 ) ⇒ Remove the ( ) through distribution,

x^4 + 8x^2 - 1 - x^2 + 3x^3 - 7x^4 ⇒ Group like terms,

Solution; 3x^3 + 7x^2 - 1

13 ) ( 3x^2 + 7xy - 2y^2 ) - ( x^2 - 6xy + 2y^2 ) ⇒ Remove the ( ) through distribution,

3x^2 + 7xy - 2y^2 -  x^2 + 6xy - 2y^2 ⇒ Group like terms,

Solution; 2x^2 + 13xy - 4y^2

14 ) ( 5x^4 - 2x^2 ) - ( 3x - 2x^2 - 4x^3 + 6x^4 ) ⇒ Remove the ( ) through distribution,

5x^4 - 2x^2  -  3x + 2x^2 + 4x^3 - 6x^4 ⇒ Group like terms,

Solution; - x^4 + 4x^3 - 3x

15 ) ( -x^2 - 9xy + 5y^2 ) - ( 4x^2 - 2xy - y^2 ) ⇒ Remove the ( ) through distribution,

- x^2 - 9xy + 5y^2 - 4x^2 + 2xy + y^2 ⇒ Group like terms,

Solution; - 5x^2 - 7xy + 6y^2

16 ) ( 4x^2y - 3xy^2 ) - ( 3x^2y - 8xy^2 ) ⇒ Remove the ( ) through distribution,

4x^2y - 3xy^2 -  3x^2y + 8xy^2 ⇒ Group like terms,

Solution; x^2y + 5xy^2

17 ) √x = 18 ⇒ Square either side,

( √x )^2 = ( 18 )^2 ⇒ Simplify,

Solution; x = 324

18 ) 3 √( 512/ 1331 ) ⇒ Take cube root of 512, and 1331,

3 √ 512 = 8, and 3 √ 1331 = 11, ⇒ Substitute,

Solution; 8 / 11

19 ) Apply Pythagorean Theorem, as such;

a^2 + b^2 = c^2,

15^2 + b^2 = 25^2,

225 + b^2 = 625,

b^2 = 400,

Solution; Length of missing side is 20 meters