179k views
1 vote
A rectangle has length (x+3)cm and width (x-2).Given that it's area is 50cm2,find the dimensions of the rectangle

1 Answer

3 votes

Answer:

length- 10cm, width- 5cm

Explanation:

You want to convert this into an algebraic equation.

Since a=lw, in this case, 50=lw. Subbing (x+3) for l and (x-2) for w, we get the equation (x+3)(x-2)=50.

Using FOIL, we can expand the brackets to make x²-2x+3x-6=50 and collect like terms to x²+x-6=50.

We want all the numbers on one side (to use the null factor law), so we subtract 50 from both sides. This gives x²+x-56=0.

From there, we factorise it, which becomes (x-7)(x+8)=0. (I used the cross method for this)

With the null factor law, one of the brackets must be equal to 0, meaning x-7=0 or x+8=0. This gives x as either 7 or -8.

With measurement, units must be positive, meaning it has to be 7. We can sub this for x in the 2 equations (length and width) to get the answers.

Length=x+3 becomes 7+3, which is 10cm.

Width=x-2 becomes 7-2, which is 5cm.

**This content involves writing, expanding, and factorising quadratic equations, and the null factor law which you may wish to revise. I'm always happy to help!

User Kokanee
by
5.8k points
Welcome to QAmmunity.org, where you can ask questions and receive answers from other members of our community.