### What's Wrong? Q7

1. (a+b)(a-b) = a^2 - b^2 not other things.

Owen here.

2. It is supposed to be -b^2 as it is a +b multiplied by -b

3. The second question should make use of algebra to find the answer .

4. You should have kind of guessed that the second question is actually trying to test you using the method in first part to solve second question...That kind of method you did we won't know if you used calculator or not also...

5. - b x b = -b^2

negative and positive = negative.

6. It should be -b^2 instead as -b* b = -b^2

7. It should be -b^2 as negative x positive = negative

8. suppose to be -b^2 since its -b mutliply by b

9. It should have been -b^2 as -b x b = -b^2

For the second part, the numbers can represent a letter.
a = 100
b = 5
You can substitue the numbers thus, you can get -b^2.

10. it should be a^2+ab-ab-b^2 instead of what is stated

11. 7b should make use of the equation in 7a, as the question states hence, which is referring to 7a

12. 7a should be -b^2. 7b should make use of 7a to find the solution

13. You must use part a to help solve

14. 1st ERROR: -b x b = -b^2, not b^2
2nd ERROR: Use the method in a) to solve b)

15. b(-b)=-b^2
Part (b) should be solved using (a+b)(a-b)-a^2

16. Question 7a should be -(b^2). You should make use of 7a to help find the answer in 7b.

17. as it is hence - you must use a method related to (a) to answer the question

18. You should be using the solution in (a) to solve (b) because they used the word HENCE

19. (a+b)(a-b) = a^2 - b^2

you need to use the method of (a) to solve (b).
If you do not, we can just press the calculator and that does not know we know the skills. So, no marks are given

20. 1. -b x b = -b^2 not b^2

21. (a) The term b^2 should be -b^2 when expanded.

(b) He did not make use of the answer in (a) to solve the question.