Answer:
a = 3
Step-by-step explanation:
First start writing out the binomial expansion of [tex](ax + 1)^7[/tex]
[tex][1^7] + [7C1 * 1^6 *(ax)] + [7C2*1^5*(ax)^2]+[7C3*1^4*(ax)^3][/tex]
as you can see from this, the last bracket will produce our [tex]x^3[/tex] term
[tex]7C3*1^4*a^3x^3 \\35a^3x^3\\35a^3 = 945\\a^3 = 27\\a = 3[/tex]
Hope this helps, let me know if you have any questions :)
