Solve the equation: x²+4x-25=-4?

x² + 4x - 21 = 0
(x + 7)(x - 3) = 0
x = 3 , x = - 7

x²+4x-25=-4
x²+4x-25+4=0
x²+4x-21=0
x²+7x-3x-21=0
x(x+7)-3(x+7)=0
(x-3)(x+7)=0

x=3, -7

x²+4x-25=-4 add 4 to both sides
x²+4x-21=0 factor this as
(x-3)(x+7)=0 So the roots are 3, -7

x^2+4x-25=-4
x^2+4x-21=0
(x+7)(x-3)=0
x=-7,3

x²+4x-25=-4
x²+4x-25 + 4=0
x²+4x-21 =0

7 * 3 = 21
7-3 = 4

(x+7)(x-3)=0

x=-7 , x=3

x^2 + 4x - 25 = -4
x^2 + 4x - 25 + 4 = 0
x^2 + 4x - 21 = 0
(x - 3)(x + 7) = 0

x - 3 = 0
x = 3

x + 7 = 0
x = -7

∴ x = 3 , x = -7

x²+4x-25=-4
x²+4x-21=0
(x+7)(x-3)=0
x=-7
x=3

First add 4 to both sides:
x² + 4x - 21 = 0

Now factor:
(x - 3)(x + 7) = 0

Answers:
x = 3, -7

x²+4x-25=-4

First add 4 to both sides:
x² + 4x - 21 = 0

Now factor:
(x - 3)(x + 7) = 0

x-3=0 and x+7=0

Answers:
x = 3, -7

Check:
3² + 4(3) - 21 = 0

9+12-21=0

0=0

(-7)² + 4(-7) - 21 = 0

49-28-21=0

0=0

ALWAYS CHECK YOUR ANSWERS TO EQUATIONS WITH MORE THAN ONE SOLUTION, AS ONE OF THE SOLUTIONS COULD BE AN EXTRANEOUS SOLUTION, BUT NOT AN ACTUAL SOLUTION!

Sherry,

To solve quadratic equations always use the following steps:

1. Move all of the factors to one side of the equation so it will equal zero.

x^2 + 4x - 25 = -4 becomes
x^2 + 4x - 25 + 4 = 0 or
x^2 + 4x - 21 = 0 from here you can either factor into the form:

(ax + n1)(bx + n2) where a, b n1 and n2 are numbers if c (21) is negative the you will have a + in the first () and a - in the second, if c is positive they can both be - or +

This problem factors out to:

(x + 7)(x - 3)

You could also use the quadratic equation once you have the equation set to zero which is

-b + and - sqrt(b^2 - 4ac)\2a so this problem would be

-4 + sqrt(4^2 - 4*1*(-21))/2 and
-4 - sqrt(4^2 - 4*1*(-21)/2 or

-4 + sqrt(100)/2 and
-4 - sqrt(100)/2 or

(-4 + 10)/2 and
(-4 - 10)/2 or

6/2 and
14/2 or

3,7