Questions on Algebra: Quadratic Equation answered by real tutors!

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Question 167807: Solve 2x ( x + 3 ) = x + 25 : Solve 2x ( x + 3 ) = x + 25
Answer by KnightOwlTutor(284) About Me  (Show Source):
You can put this solution on YOUR website!
Use the distributive property to multiply the first part of the equation.
2x^2+6x=x+25
subtract x from both sides
2x^2+5x=25
Subtract 25 from both sides
2x^2+5x-25=0
this is a quadratic equation
Solved by pluggable solver: SOLVE quadratic equation with variable
Quadratic equation ax^2+bx+c=0 (in our case 2x^2+5x+-25 = 0) has the following solutons:

x[12] = (b+-sqrt( b^2-4ac ))/2\a

For these solutions to exist, the discriminant b^2-4ac should not be a negative number.

First, we need to compute the discriminant b^2-4ac: b^2-4ac=(5)^2-4*2*-25=225.

Discriminant d=225 is greater than zero. That means that there are two solutions:  x[12] = (-5+-sqrt( 225 ))/2\a.

x[1] = (-(5)+sqrt( 225 ))/2\2 = 2.5
x[2] = (-(5)-sqrt( 225 ))/2\2 = -5

Quadratic expression 2x^2+5x+-25 can be factored:
2x+5x+-25 = 2(x-2.5)*(x--5)
Again, the answer is: 2.5, -5. Here's your graph:
graph( 500, 500, -10, 10, -20, 20, 2*x^2+5*x+-25 )