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Find constants - Mathematics?
A maths problem
Find constants a, b and c such that, for all values of x,
3x² - 5x + 1 = a(x+b)² + c
Hence find the coordinates of the vertex on the graph of y=3x² - 5x + 1
Working and description helpful
Thanks
3 Answers
- Simon van DijkLv 68 years agoFavorite Answer
3x² - 5x + 1 = a(x+b)² + c
3x² - 5x + 1 = ax² + 2ab.x + a.b² + c
this is only possible if all powers of x vanish so:
a = 3
this gives
- 5x + 1 = + 6b.x + 3.b² + c
so b = -5/6
this gives
+ 1 = + 25/12 + c
so c = -13/12
You can find the vertex (lowest value) of y = 3x² - 5x + 1 by differentiating
dy/dx = 0 = 6.x - 5 so at x = 5/6
- icemanLv 78 years ago
y = 3(x^2 - 5/3*x + (5/6)^2) + 1 - 25/36
y = 3(x - 5/6)^2 - 13/12 => in vertex form of : a(x - h)^2 + k, where (h , k) is the vertex:
vertex at(5/6 , -13/12)
- DWReadLv 78 years ago
y = 3x² - 5x + 1
you want to convert it to "vertex form," y = a(x - h)² + k
factor out the leading coefficient
y = 3(x² -(5/3)x) + 1
complete the square
coefficient of x term: -5/3
divide coefficient in half: -5/6
square it: (5/6)²
use (5/6)² to complete the square:
y = 3(x² -(5/3)x + (5/6)²) - 3(5/6)² + 1
= 3(x - 5/6)² - 3(5/6)² + 1
= 3(x - 5/6)² - 13/12
vertex (5/6, -13/12)