To solve this problem you must apply the proccedure shown below:
1. You have to apply the distributive property to the expression shown above and you need to remember that you must sum the exponents when you multilpy equal bases.
2. Keeping the information above on mind, you have:
[tex] -2x^{4}(-4x^{b}-2x^{3}+5x)\\ 8x^{4b} +4x^{7} -10x^{5} [/tex]
Therefore, the answer is: [tex] 8x^{4b} +4x^{7} -10x^{5}
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