Processing math: 100%

User interface language: English | Español

Date November 2017 Marks available 5 Reference code 17N.2.hl.TZ0.7
Level HL only Paper 2 Time zone TZ0
Command term Find Question number 7 Adapted from N/A

Question

In the quadratic equation 7x28x+p=0, (pQ), one root is three times the other root.
Find the value of p.

Markscheme

METHOD 1

let roots be α and 3α     (M1)

sum of roots (4α)=87     M1

α=27     A1

EITHER

product of roots (3α2)=p7     M1

p=21α2=21×449

OR

7(27)28(27)+p=0     M1

47167+p=0

THEN

p=127 (=1.71)     A1

 

METHOD 2

x=8±6428p14     (M1)

8+6428p14=3(86428p14)     M1A1

8+6428p=2436428p6428p=4     (M1)

p=127 (=1.71)     A1

[5 marks]

Examiners report

[N/A]

Syllabus sections

Topic 2 - Core: Functions and equations » 2.6 » Use of the discriminant Δ=b24ac to determine the nature of the roots.

View options