I'm really struggling with this problem can someone please give me an examples like this problem or explain how to solve it an problems like it.

Step-by-step explanation:

Ok so I'm not 100% sure how to solve this but what I would do is use the equation a^2 + b^2 = c^2 this equation is used to solve for the hypotenuse or the longest side of a triangle. To find a^2 you would do (21+15)^2 (Also this symbol ^ is the power symbol) and the answer would be 1296. b^2 would be 25^2 or 625. The equation turns out to be 1296 + 625 = c^2. c^2 (or x in this case) would be 1921. To find just c and not c^2 you would find the square root of 1921 which is 43.8292140016 or if rounded would be 43.8. Also this might not help if I misinterpreted the question...

the first one is x^2+2x+2

the second one is x^2+4

the last one is x^2-4x+8

-8/2y-8=5/y+4-7y+8/y^2-16

we move all terms to the left:

-8/2y-8-(5/y+4-7y+8/y^2-16)=0

we can not solve this equation