Question

When the solution of x2 + 9x − 9 is expressed as 9 plus or minus the square root of r, all over 2, what is the value of r? x equals negative b plus or minus the square root of b squared minus 4 times a times c, all over 2 times a

A: 117
B: 54
C:45
D: 9

Answer 1

117

Explanation:

Answer 2

The answer is option A. 117

Explanation:

The general solution of the quadratic equation is:

`x=(-b \pm √(b^2-4ac) )/(2a)`

The given equation is x2 + 9x − 9 is expressed as minus 9 plus or minus the square root of r, all over 2

Comparing to the general solution

∴ r = determinant = b² - 4 a c

From the given equation: a = 1 , b = 9 and c = -9

∴ r = 9² - 4 * 1 * (-9) = 81 + 36 = 117

The answer is option A. 117