Final answer:
In multiplying \(x^4\) by \((x-21)\), distribute \(x^4\) across the parentheses to get \(x^5\) and \(-21x^4\). Combining these yields \(x^5 - 21x^4\), represented by option A. This result is derived by applying the distributive property and combining like terms in the multiplication of the expressions.
Step-by-step explanation:
The expression ion(x⁴)(x-21) is not correctly transcribed, but if we assume the question is to multiply x⁴ by (x-21), then the solution would be as follows: To multiply these two expressions, you distribute x⁴ across the parentheses as such: x⁴ × x = x⁵ (since x⁴ × x¹ = x⁴+1), x⁴ × -21 = -21x⁴ (since you just multiply the coefficient by the constant -21). Combining these two parts gives us the resultant expression: x⁵ - 21x⁴. So the correct answer is A. x⁵ - 21x⁴.