Ask Singapore Homework?
Upload a photo of a Singapore homework and someone will email you the solution for free.
Question
secondary 2 | Maths
One Answer Below
Anyone can contribute an answer, even non-tutors.
TIA!
Date Posted: 2 years ago
Views: 277
One idea is as follows.
k² - 3k + 5 = 0
k² - 3k = -5
Squaring both sides,
(k² - 3k)² = (-5)²
(k² - 3k)² = 25
We can do rainbow expansion on (k² - 3k)² or some other suitable approach, unless you can expand it mentally in your head!
k⁴ - 3k³ - 3k³ + 9k² = 25
k⁴ - 6k³ + 9k² = 25
All we need to do is to subtract both sides by 7.
k⁴ - 6k³ + 9k² - 7 = 25 - 7
k⁴ - 6k³ + 9k² - 7 = 18
So the value of k⁴ - 6k³ + 9k² - 7 is 18.
k² - 3k + 5 = 0
k² - 3k = -5
Squaring both sides,
(k² - 3k)² = (-5)²
(k² - 3k)² = 25
We can do rainbow expansion on (k² - 3k)² or some other suitable approach, unless you can expand it mentally in your head!
k⁴ - 3k³ - 3k³ + 9k² = 25
k⁴ - 6k³ + 9k² = 25
All we need to do is to subtract both sides by 7.
k⁴ - 6k³ + 9k² - 7 = 25 - 7
k⁴ - 6k³ + 9k² - 7 = 18
So the value of k⁴ - 6k³ + 9k² - 7 is 18.
Thx so much Eric Nicholas K!
See 1 Answer
360 Tutoring Program