Explanation:
(7a-5) (3a+4)
1) you need to multiply 7a with 3a its mean you get 21a ²
2) you need to multiply 7a with +4 and you will get +28a
3) you need to multiply -5 with +3a and you will get -15a
4) you need to multiply -5 with +4 and you will get -20
5) you need to combine all of this number and you will get an equation :
21a²+28a-15a-20
6) you need to look for the like terms and simplified it . in this equation, we can see that +28a and -15 a is the like terms because have a. so you need to simplified it:
+28a - 15a = 13a
7) and you will get the final answer:
= 21a² + 13a - 20
p/s : let me know if you want the explanation for solving this equation. that was a simplify explanation. thank you :)