Ask Singapore Homework?
Upload a photo of a Singapore homework and someone will email you the solution for free.
Question
secondary 4 | A Maths
One Answer Below
Anyone can contribute an answer, even non-tutors.
hi can someone help me check if there's an error in ans answer key.
for the value of p and q
p i got 1 while q I got 0, a I got 3.
no matter how I try i can't get the ans key answer q is - 42
See 1 Answer
It is likely that 1 mark will be deducted from the working for this inaccuracy, since truncating the expansion without "+..." means that the expansion of the terms stops there.
= (1 + 4ax + 6(ax)² + ...)(1 + 3(-4x) + 3(-4x)² +...)
= (1 + 4ax + 6a²x² +...)(1 - 12x + 48x² +...)
= 1 - 12x + 48x² + 4ax - 48ax² + 6a²x² +...
= 1 + (4a - 12)x + (48 - 48a + 6a²)x² +...
(You may also use the ≈ sign if you don't want to write the +...)
Since the first 2 terms are p and qx²,
p = 1
4a - 12 = 0
4a = 12
a = 3
q = 48 - 48(3) + 6(3²)
= 48 - 144 + 54
= -42