Answer:
21x^4 + 8x + 7
Explanation:
This is the answer because:
1) Simplify each term and multiply like terms and multiply them because in order to find the area we have to multiply the height and width.
2) Since we have to multiply like terms, 7x^2 and 3x^2 are the only like terms. Therefore, we multiply 7x^2 * 3x^2 = 21x^4.
3) The rest of the numbers are not like terms.
4) Therefore, the answer is 21x^4 + 8x + 7
Hope this helps!