solve by quadratic equation?

Question

x^2-4x-11=0 and 3x^2+4x = 7

Answer 1

Question 1
x = [ 4 ± √(16 + 44) ] / 2
x = [4 ± √60 ] / 2
x = [4 ± 2√15 ] / 2
x = 2 ± √15

Question 2
x = [ - 4 ± √(16 + 84) ] / 6
x = [- 4 ± √100 ] / 6
x = [- 4 ± 10 ] / 6
x = 1 , x = - 7 / 3

Answer 2

You mean solve the given quadratic equations by using the quadratic formula? This is the quadratci formula:
x = [ -b ± √(b^2 - 4ac) ] / 2a

For the first one, a=1, b = -4, c = -11. This gives us
x = [ 4 ± √(16 + 44) ] / 2
x = [ 4 ± √60 ] / 2
x = [ 4 ± √(4*15)] / 2
x = [ 4 ± 2√15] / 2
x = 2 ± √15
x = 2+√15 and 2-√15

For the second one, a=3, b=4, c= -7 (we have to bring the 7 to the left side so that the equation is in the form of ax^2 + bx + c = 0). So just use the formula again.

Answer 3

If you can't remember the quadratic equation, go on youtube to this adress:

http://youtube.com/watch?v=43JvqjHtFXQ

Answer 4

those equations are already in quadraitic form. just plug in the variables. you just have to get an equaiton down to quad form and recognize it. it will come up time and time again. same with linear, they just pop up all the time and your job is to recognize it when you see it!

Answer 5

[4 +/- sqrt((-4)^2 - 4(1)(-11))] / (2)(1)
[4 +/- sqrt(60)] / 2
[4 +/- 2sqrt(15)] / 2
2 +/- sqrt(15)
5.873 or -1.873

See above for explanation:
1 or -2.333