Solve rational equations

To solve a rational equation, first clear the fractions, by multiplying both sides by the denominators or by the lowest common denominator (LCD). Then solve for the variable.

Learn with an example

Solve for w.

-4/w-8 = -2/w+1

w = ________ or w = ___________

Solve for w.

-4/w-8 = -2/w+1

-4[(w-8)(w+1)]/w-8 = -2[(w-8)(w+1)]/w+1 Multiply both sides by (w − 8)(w + 1)

-4(w+1) = -2(w-8) Simplify

-4w-4 = -2w+16 Apply the distributive property

-2w-4 = 16 Add 2w to both sides

-2w = 20 Add 4 to both sides

w = -10 Divide both sides by 2

Now check whether this is an extraneous solution. Plugging w = -10 into the first denominator, w-8 , yields -18 . Plugging w = -10  into the second denominator, w+1 , yields -9 .Since neither denominator is 0, which would be undefined, this is a valid solution.

The solution is w = -10

Solve for u.

8/u+3 = 3/u-2

u = ________ or u = ___________

Solve for u.

8/u+3 = 3/u-2

8[(u+3)(u-2)]/u+3 = 3[(u+3)(u-2)]/u-2 Multiply both sides by (u + 3)(u − 2)

8(u-2) = 3(u+3) Simplify

8u-16 = 3u+9 Apply the distributive property

5u-16 = 9 Subtract 3u from both sides

5u = 25 Add 16 to both sides

u = 5 Divide both sides by 5

Now check whether this is an extraneous solution. Plugging u = 5 into the first denominator, u+3 , yields 8. Plugging u = 5 into the second denominator, u-2, yields 3  Since neither denominator is 0, which would be undefined, this is a valid solution.

The solution is u = 5

Solve for k.

k-8/6 = k-10/7

k = ________ or k= ___________

Solve for k.

k-8/6 = k-10/7

(k-8)(6 . 7) / 6 = (k-10)(6 .7)/7 Multiply both sides by 6 · 7

7(k-8) = 6(k-10) Simplify

7k-56 = 6k-60 Apply the distributive property

k-56 = -60 Subtract 6k from both sides

k = -4 Add 56 to both sides

Now check whether this is an extraneous solution. Since neither denominator is 0, which would be undefined, this is a valid solution.

The solution is k = -4

let’s practice!