Solve rational equations
Key Notes :
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
There may be 1 or 2 solutions.
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
There may be 1 or 2 solutions.
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
There may be 1 or 2 solutions.
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!