Question

Which equation has the solutions x= 5 ± 2 square root 7 all over 3

1. 3x2 – 5x + 7 = 0
2. 3x2 – 5x – 1 = 0
3. 3x2 – 10x + 6 = 0
4. 3x2 – 10x – 1 = 0

Answer 1

D

Explanation:

Using the equation, you see that 3x^2-10x-1=0

the answer is d

Answer 2

4. 3x^2 – 10x – 1 = 0

Explanation:

You can write the quadratic from the roots:

0 = (x - (5-2√7)/3)(x - (5+2√7)/3)

= (x -5/3)^2 -(2√7/3)^2

= x^2 - 10/3x +25/9 -28/9

= x^2 -10/3x -1/3

Multiplying by 3 gives ...

0 = 3x^2 -10x -1