Answer:
55x^4+25x^3+35x^2
Explanation:
5x²(4x^2+8x-1 and 7x^2-3x+8)
Applying distribution property,we have 
- 5x^2(4x^2+8x-1 + 7x^2-3x+8)
 - (5x^2)*(4x^2)+(5x^2)*(8x)+(5x^2)*(-1)+(5x^2)(7x^2)+(5x^2)*(-3x)+(5x^2)*(8)
 
Simplifying them,we have 
- 20x^4+40x^3−5x^2+35x4−15x^3+40x^2
 - 55x^4+25x^3+35x^2