What is the formula to solve quadratic equations

I can't understand it.
Please explain in details.
thanks.

Here is the basic format of a quadratic equation:
ax^2 + bx + c = 0

a = coefficient of x^2
b = coefficient of x
c = a constant

so remember above!

now the quadratic formula, which includes all above a, b, c, is as follows:

x = [ -b +/- sqrt (b^2 - 4ac)] / 2a

so anytime you get a quadratic equation, use the above formula to find the values of x.

Standard Form:
ax^2+bx+c = 0

Quadratic Formula:
x = -b+-√(b^2-4ac) / 2a
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For example, solve for x in the equation 3x+4x^2-8=0.

Get the equation into standard form:
4x^2+3x-8 = 0

Use the quadratic formula. In this problem: a=4, b=3, and c=-8. Plug those in.
x = -b+-√(b^2-4ac) / 2a
x = -(3)+-√((3)^2-4(4)(-8)) / 2(4)
x = -3+-√(9+128) / 8
x = -3+-√137 / 8

Answer: x=(-3+√137)/8 or x=(-3-√137)/8
*You can use a calculator to get the answers in decimal form if you'd like.

http://latex.codecogs.com/png.latex?\large%20\dpi{300}%20\bg_white%20ax^2+bx+c=0;%20x_{1,2}=\frac{-b\pm%20\sqrt{b^2-4ac}}{2a}