OG详解-OG3 数学2 Q8

Choice A is correct. Since x  is a factor of each term in the given expression, the expression is equivalent to  x(9x)+ x(5), or x (9x +5).
Choice B is incorrect. This expression is equivalent to 45x² +5x , not 9x² +5x. Choice C is incorrect. This expression is equivalent to  9x² + 45x , not 9x² +5x. Choice D is incorrect. This expression is equivalent to 9x³ +5x² , not 9x² +5x.