SOLUTION: child a is 4 years older than b. the product of their ages is 140. the equation is x(x-4)=140 how do you solve for x?

Question 218658: child a is 4 years older than b. the product of their ages is 140.
the equation is x(x-4)=140
how do you solve for x?
Answer by drj(1380) (Show Source): You can put this solution on YOUR website!
Child a is 4 years older than b. The product of their ages is 140.

The equation is x(x-4)=140

how do you solve for x?

Step 1. Form a quadratic equation to get . Then subtract 140 from both sides of the equation

Or x=-10 and x=14. We need to select x=14 for positive ages.

ANSWER: x is 14 hears old

Step 2. We can also se the quadratic formula given as

where a=1, b=-4 and c=-140

Solved by pluggable solver: SOLVE quadratic equation with variable

Quadratic equation (in our case ) has the following solutons:

For these solutions to exist, the discriminant should not be a negative number.

First, we need to compute the discriminant : .

Discriminant d=576 is greater than zero. That means that there are two solutions: .

Quadratic expression can be factored:

Again, the answer is: 14, -10. Here's your graph:

Same result as before...

I hope the above steps were helpful.

For FREE Step-By-Step videos in Introduction to Algebra, please visit http://www.FreedomUniversity.TV/courses/IntroAlgebra and for Trigonometry visit http://www.FreedomUniversity.TV/courses/Trigonometry.

Good luck in your studies!

Respectfully,
Dr J

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