Posted by **toni** on Tuesday, October 8, 2013 at 12:41pm.

Im lost i don't know how to do this can someone show me step by step how to solve this

For what value of c does the equation have one real root? Hint using the values of a and b found in the equation, solve D = 0 for c.

Consider the quadratic expression X^2 + 4x + c = 0.

- algebra -
**Jai**, Tuesday, October 8, 2013 at 12:53pm
Recall the formula for discriminant. For a quadratic equation in the general form, ax^2 + bx + c = 0,

D = b^2 - 4ac

if

D = 0 : real, equal/double root

D > 0 : two real, unequal roots

D < 0 : two imaginary roots

Since we're required to have one real root, we equate D to zero, and solve for the unknown, c.

x^2 + 4x + c = 0

a = 1

b = 4

c = ?

Substituting to the discriminant formula, (D = 0)

0 = 4^2 - 4*1*c

0 = 16 - 4c

4c = 16

c = 4

Hope this helps~ :3

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