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solve for x

What is the volume of a rectangular prism if the length is 10.4 mm the width is 5 mm in the height is 8 mm

This is my question~~ ( r ^ 4 - 2r ^ 3 - 23 r ^ 2 - 4r - 32)÷(r+4) ~~ i must use long division to solve it : / i was wondering if anyone world like to solve it. and if so, share step-by-step explanations! you! ❤

Y= a(x-3)squared-1 what is the value of a