You simply multiply the two and distribute to solve. I am starting with t(x) because I think it is easier.
(x+4)*(2x^2+3x-4)
2x^3+3x^2-4x+8x^2+12x-16 (distribute)
2x^3+11x^2+8x-16 (combine like terms)
I’ll help you a bit and yea
5^23 - 5^21 = 5^(21+2) - 5^21
5^23 - 5^21 = 5^21*5^2 - 5^21*1
5^23 - 5^21 = 5^21*(5^2 - 1)
5^23 - 5^21 = 5^21*(25 - 1)
5^23 - 5^21 = 5^21*24
5^23 - 5^21 = 24*5^21
5^23 - 5^21 = 24*k
The original number is in the form 24k where k = 5^21, so this proves that the original number is a multiple of 24
-0.03125 this would be the answer to that problem