Using the completing-the-square method, find the vertex of the function f(x) = 2x2 − 8x + 6 and indicate whether it is a minimum or a maximum and at what point.

Question

welshfella · Answer

first divide through by 2
= 2( x^2 - 4x + 3)

can you continue ?

james1769 · Answer

kinda

welshfella · Answer

complete the square on what is in the parenthese

= 2( x - 2)^2 - A + 3)

can you work out what A is?

james1769 · Answer

a is 1?

welshfella · Answer

the -2 came from dividing the -4 in 4x by 2  Now you have to correct for the last term in the expansion of (x - 2)^2

welshfella · Answer

(x - 2)^2 = x^2 - 4x +  what?

welshfella · Answer

no, not 1

welshfella · Answer

(x - 2)(x - 2) = x^2 - 2x - 2x -2 * -2

welshfella · Answer

sorry guy gotta go right now

- the last term is -2*-2 = +4

so A = 4

james1769 · Answer

oh thats right

james1769 · Answer

Maximum at (2, −2)
	Minimum at (2, −2)
	Maximum at (2, 6)
	Minimum at (2, 6)
but which one is right?