Date | May 2022 | Marks available | 2 | Reference code | 22M.1.SL.TZ1.1 |
Level | Standard Level | Paper | Paper 1 (without calculator) | Time zone | Time zone 1 |
Command term | Find | Question number | 1 | Adapted from | N/A |
Question
Consider the points A(-2, 20)A(−2, 20), B(4, 6)B(4, 6) and C(-14, 12)C(−14, 12). The line LL passes through the point AA and is perpendicular to [BC][BC].
Find the equation of LL.
The line LL passes through the point (k, 2)(k, 2).
Find the value of kk.
Markscheme
mBC=12-6-14-4 (=-13)mBC=12−6−14−4 (=−13) (A1)
finding mL=-1mBCmL=−1mBC using their mBCmBC (M1)
mL=3mL=3
y-20=3(x+2), y=3x+26y−20=3(x+2), y=3x+26 A1
Note: Do not accept L=3x+26L=3x+26
[3 marks]
substituting (k, 2)(k, 2) into their LL (M1)
2-20=3(k+2)2−20=3(k+2) OR 2=3k+262=3k+26
k=-8k=−8 A1
[2 marks]
Examiners report
Finding the gradient of a line was well understood and many candidates also correctly found the perpendicular slope. Even with an error in their part (a), follow through marks in part (b) allowed many candidates to earn full marks for finding k despite their incorrect equation resulting in arithmetic of greater complexity.