Answer:
a) -2n+14
b) -5n+30
Step-by-step explanation:
a) 12 to 10 to 8 etc. is -2 each time.
Since this is linear, so the first part is therefore -2n. To get from -2 to 12, you have to add 14. So the expression is -2n+14. Now, to prove this, we can input 5 where n is to find the 5th term, which should be 4. -2x5 = -10. -10+14 = 4. The expression is proven correct.
b) 25 to 20 to 15 etc. is -5 each time.
This is also linear, so the first part is therefore -5n. To get from -5 to 25, you have to add 30. So the expression is -5n+30. We can prove this similar to question A. We input 5 where n is to find the 5th term which should be 5. -5x5 = -25. -25+30 = 5. The expression is proven correct.
