Examples with solutions for The Quadratic Formula: Applying the formula with two solutions

Exercise #1

Solve the following equation:

x2+5x+4=0 x^2+5x+4=0

Video Solution

Step-by-Step Solution

The parameters are expressed in the quadratic equation as follows:

aX2+bX+c=0

 

We substitute into the formula:

 

-5±√(5²-4*1*4) 
          2

 

-5±√(25-16)
         2

 

-5±√9
    2

 

-5±3
   2

 

The symbol ± means that we have to solve this part twice, once with a plus and a second time with a minus,

This is how we later get two results.

 

-5-3 = -8
-8/2 = -4

 

-5+3 = -2
-2/2 = -1

 

And thus we find out that X = -1, -4

Answer

x1=1 x_1=-1 x2=4 x_2=-4

Exercise #2

Solve the following equation:

2x210x12=0 2x^2-10x-12=0

Video Solution

Step-by-Step Solution

Let's recall the quadratic formula:

Quadratic formula | The formula

We'll substitute the given data into the formula:

x=(10)±10242(12)22 x={{-(-10)\pm\sqrt{-10^2-4\cdot2\cdot(-12)}\over 2\cdot2}}

Let's simplify and solve the part under the square root:

x=10±100+964 x={{10\pm\sqrt{100+96}\over 4}}

x=10±1964 x={{10\pm\sqrt{196}\over 4}}

x=10±144 x={{10\pm14\over 4}}

Now we'll solve using both methods, once with the addition sign and once with the subtraction sign:

x=10+144=244=6 x={{10+14\over 4}} = {24\over4}=6

x=10144=44=1 x={{10-14\over 4}} = {-4\over4}=-1

We've arrived at the solution: X=6,-1

Answer

x1=6 x_1=6 x2=1 x_2=-1

Exercise #3

Solve the following equation:

x2+9x+8=0 x^2+9x+8=0

Video Solution

Answer

x1=1 x_1=-1 x2=8 x_2=-8

Exercise #4

Solve the following equation:

x23x+2=0 x^2-3x+2=0

Video Solution

Answer

x1=1,x2=2 x_1=1,x_2=2

Exercise #5

Solve the following:

x2+5x+4=0 x^2+5x+4=0

Video Solution

Answer

x1=1,x2=4 x_1=-1,x_2=-4

Exercise #6

Solve the following equation:

5x26x+1=0 5x^2-6x+1=0

Video Solution

Answer

x1=1,x2=15 x_1=1,x_2=\frac{1}{5}

Exercise #7

What is the value of X in the following equation?

X2+10X+9=0 X^2+10X+9=0

Video Solution

Answer

x1=1,x2=9 x_1=-1,x_2=-9

Exercise #8

Solve the following equation:

x24x+4=0 x^2-4x+4=0

Video Solution

Answer

x=2 x=2

Exercise #9

Solve the following equation:

4x26x4=0 4x^2-6x-4=0

Video Solution

Answer

x1=2,x2=12 x_1=2,x_2=-\frac{1}{2}

Exercise #10

Solve the following equation:

x22x3=0 x^2-2x-3=0

Video Solution

Answer

x1=3,x2=1 x_1=3,x_2=-1

Exercise #11

Solve the following equation:

x2+5x+6=0 x^2+5x+6=0

Video Solution

Answer

x1=3,x2=2 x_1=-3,x_2=-2

Exercise #12

Solve the following equation:

x2+3x18=0 x^2+3x-18=0

Video Solution

Answer

x1=3,x2=6 x_1=3,x_2=-6

Exercise #13

Solve the following equation:

x2+10x+21=0 x^2+10x+21=0

Video Solution

Answer

x1=3,x2=7 x_1=-3,x_2=-7

Exercise #14

Solve for X:

2X2+6X+8=0 -2X^2+6X+8=0

Video Solution

Answer

X1=4,X2=1 X_1=4, X_2=-1

Exercise #15

Solve the following equation:


x2x20=0 x^2-x-20=0

Video Solution

Answer

x1=4,x2=5 x_1=-4,x_2=5

Exercise #16

Solve the following equation:

3x2+10x8=0 3x^2+10x-8=0

Video Solution

Answer

x1=23,x2=4 x_1=\frac{2}{3},x_2=-4

Exercise #17

Solve the following equation:

2x2+22x60=0 -2x^2+22x-60=0

Video Solution

Answer

x1=5 x_1=5 x2=6 x_2=6

Exercise #18

Solve the following equation:

x2+10x+25=0 x^2+10x+25=0

Video Solution

Answer

x=5 x=-5

Exercise #19

Solve the following equation:

x2+10x21=0 -x^2+10x-21=0

Video Solution

Answer

x1=7,x2=3 x_1=7,x_2=3

Exercise #20

Solve the equation

3x239x90=0 3x^2-39x-90=0

Video Solution

Answer

x1=15 x_1=15 x2=2 x_2=-2