Quadratic Equation Formula

[匿名]

2009-03-04 1:51 am

My teacher said when doing this

x = (-b +_ √(b^2 - 4ac) / 2a
We have to plug in the coefficients.

What are coefficients? (No copy and paste)
How to find them? Let's say if we are doing this:

2x^2 - x = 3

Thanks a lot

回答 (1)

用戶2053

2009-03-04 2:20 am

✔ 最佳答案

For a equation ax^2 + bx + c = 0

we call a , b , c are coefficients of this equation,where a is the coefficient of x^2 , b is the coefficient of x, c is the constant.

Since 2x^2 - x = 3 can rewrite as : 2x^2 - 1x - 3 = 0
So the coefficients of this equation is a=2 for x^2, b= - 1 for x, c= - 3 is the constant.

To slove it , We have to plug in the coefficients a=2 , b= -1 ,c= -3 to
x = (-b +_ √(b^2 - 4ac) / 2a

x = {- -1 ± √[ -1^2 - 4(2)(-3)]} / 2(2)

x = (1 ± √25)/4

x = 3/2 or -1

2009-03-03 18:23:54 補充：
x = {- -1 ± √[ -1^2 - 4(2)(-3)]} / 2(2)

should be x = {- -1 ± √[ (-1)^2 - 4(2)(-3)]} / 2(2)

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