5x^2+21x-8=0

Simple and best practice solution for 5x^2+21x-8=0 equation. Check how easy it is, and learn it for the future. Our solution is simple, and easy to understand, so don`t hesitate to use it as a solution of your homework.

If it's not what You are looking for type in the equation solver your own equation and let us solve it.

Solution for 5x^2+21x-8=0 equation:


Simplifying
5x2 + 21x + -8 = 0

Reorder the terms:
-8 + 21x + 5x2 = 0

Solving
-8 + 21x + 5x2 = 0

Solving for variable 'x'.

Begin completing the square.  Divide all terms by
5 the coefficient of the squared term: 

Divide each side by '5'.
-1.6 + 4.2x + x2 = 0

Move the constant term to the right:

Add '1.6' to each side of the equation.
-1.6 + 4.2x + 1.6 + x2 = 0 + 1.6

Reorder the terms:
-1.6 + 1.6 + 4.2x + x2 = 0 + 1.6

Combine like terms: -1.6 + 1.6 = 0.0
0.0 + 4.2x + x2 = 0 + 1.6
4.2x + x2 = 0 + 1.6

Combine like terms: 0 + 1.6 = 1.6
4.2x + x2 = 1.6

The x term is 4.2x.  Take half its coefficient (2.1).
Square it (4.41) and add it to both sides.

Add '4.41' to each side of the equation.
4.2x + 4.41 + x2 = 1.6 + 4.41

Reorder the terms:
4.41 + 4.2x + x2 = 1.6 + 4.41

Combine like terms: 1.6 + 4.41 = 6.01
4.41 + 4.2x + x2 = 6.01

Factor a perfect square on the left side:
(x + 2.1)(x + 2.1) = 6.01

Calculate the square root of the right side: 2.451530134

Break this problem into two subproblems by setting 
(x + 2.1) equal to 2.451530134 and -2.451530134.

Subproblem 1

x + 2.1 = 2.451530134 Simplifying x + 2.1 = 2.451530134 Reorder the terms: 2.1 + x = 2.451530134 Solving 2.1 + x = 2.451530134 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.1' to each side of the equation. 2.1 + -2.1 + x = 2.451530134 + -2.1 Combine like terms: 2.1 + -2.1 = 0.0 0.0 + x = 2.451530134 + -2.1 x = 2.451530134 + -2.1 Combine like terms: 2.451530134 + -2.1 = 0.351530134 x = 0.351530134 Simplifying x = 0.351530134

Subproblem 2

x + 2.1 = -2.451530134 Simplifying x + 2.1 = -2.451530134 Reorder the terms: 2.1 + x = -2.451530134 Solving 2.1 + x = -2.451530134 Solving for variable 'x'. Move all terms containing x to the left, all other terms to the right. Add '-2.1' to each side of the equation. 2.1 + -2.1 + x = -2.451530134 + -2.1 Combine like terms: 2.1 + -2.1 = 0.0 0.0 + x = -2.451530134 + -2.1 x = -2.451530134 + -2.1 Combine like terms: -2.451530134 + -2.1 = -4.551530134 x = -4.551530134 Simplifying x = -4.551530134

Solution

The solution to the problem is based on the solutions from the subproblems. x = {0.351530134, -4.551530134}

See similar equations:

| 32+2x=24-8x | | -16/b=-4 | | 4a-9b^2=4a^2-2b | | -10+10=0 | | 7.5x^2-0.2412x=0 | | 4n=-n^2-4 | | 11x+12=56 | | C(x)=0.0002x^2+24 | | 7.5x^2-0.2412=0 | | 20x=24x+17 | | 8g-4=7g+6 | | 4x+5y=115 | | -8x=-12-x^2 | | -30w^7+15w^7= | | 21j=16(j-8) | | h=-16t^2+169t+35 | | -6(y-4)=12 | | y=4-3/7 | | 4d-2d=12 | | 4j+4=3j+8 | | 6m=9m-3m | | 5-t=4 | | (m+2)+3ni=5-12i | | y=7x-4/7 | | 6xsquared+15=33 | | -5(-4)=-4/-2 | | y=0.2x+0.5 | | 12a^4+(-29a^4)= | | 8-5m-10m=18-2m | | 7+30x=15x+34 | | Y=sqrt(14*X+10)-SQRT(7*x-15) | | -8-12d-6d^2+3.5d^3=0 |

Equations solver categories