Subject: Compulsory Maths
As we know that 1, 2, \(\frac{1}{2}\),\(\frac{-4}{5}\), etc are the rational numbers. Similarly,\(\frac{x}{2}\),\(\frac{x^2}{y^2}\),\(\frac{x+3}{x-8}\), etc. are called rational expressions. Here we shall discuss about addition, subtraction,multiplication and division of rational expressions.
Multiplication of Rational Expressions
In multiplication, we simplify the numerical coefficients as in a case of multiplication of fraction. In the case of variables, we apply the product and quotient rules of indices. In a division, we should multiply the dividend by the reciprocal of a division. For example,
\(\frac{4a^3b^2}{5a^3y^3}\)×\(\frac{10x^4y^3}{12a^4b}\)
\(\frac{2x^{4-3}× y^{3-2}}{3a^{4-3}×b^{3-2}}\)
\(\frac{2xy}{3ab}\)ans.
Addition and Subtraction of Rational Expression with the different denominators
In this case, we should find the LCM of the denominators. Then the LCM is divided by each denominator and the quotient is multiplied by the corresponding numerator as in a case of simplification of unlike fraction. For example,
\(\frac{x}{2}\) +\(\frac{x}{6}\)
\(\frac{3x+x}{6}\) =\(\frac{4x}{6}\) =\(\frac{2x}{3}\) ans.
Multiply: \(\frac{4a^3b^2}{5x^3y^2}\) × \(\frac{10x^4y^3}{12a^4b^3}\)
Solution:
\(\frac{4a^3b^2}{5x^3y^2}\) × \(\frac{10x^4y^3}{12a^4b^3}\)
= \(\frac{4a^3b^2×10x^4y^3}{5x^3y^2×12a^4b^3}\)
= \(\frac{2x^{4-3}×y^{3-2}}{3a^{4-3}b^{3-2}}\)
= \(\frac{2xy}{3ab}\)
Divide: \(\frac{5x^2}{8ax^3}\) ÷ \(\frac{15a^3y^3}{16a^2x^2}\)
Solution:
= \(\frac{5x^2}{8ax^3}\) ÷ \(\frac{15a^3y^3}{16a^2x^2}\)
= \(\frac{5x^2}{8ax^3}\) × \(\frac{15a^3y^3}{16a^2x^2}\)
= \(\frac{2a^2x^4y}{3a^4x^3y^3}\)
= \(\frac{2x^{4-3}}{3a^{4-2}y^{3-1}}\)
= \(\frac{2x}{3a^2y^2}\)
Simplify: \(\frac{6y^2}{4x^2}\) × \(\frac{2x^3}{3y^3}\) ÷ \(\frac{5xy}{6ab}\)
Solution:
\(\frac{6y^2}{4x^2}\) × \(\frac{2x^3}{3y^3}\) ÷ \(\frac{5xy}{6ab}\)
\(\frac{6y^2}{4x^2}\) × \(\frac{2x^3}{3y^3}\) × \(\frac{6ab}{5xy}\)
\(\frac{6abx^3y^2}{5x^3y^4}\)
\(\frac{6ab}{5y^{4-2}}\)
\(\frac{6ab}{5y^2}\)
Simplify quickly: \(\frac{x^2}{a^2}\) × \(\frac{a}{x}\)
Solution:
Here, \(\frac{x^2}{a^2}\) × \(\frac{a}{x}\)
= \(\frac{x^2a}{a^2x}\)
= \(\frac{x}{a}\) ans.
Divide: \(\frac{a^3}{x^3}\) ÷ \(\frac{a^2}{x^2}\)
Solution:
Here, \(\frac{a^3}{x^3}\) ÷ \(\frac{a^2}{x^2}\)
= \(\frac{a^3}{x^3}\) × \(\frac{x^2}{a^2}\)
= \(\frac{a^3x^2}{x^3a^2}\)
= \(\frac{a}{x}\) ans.
Add: \(\frac{x}{2}\) + \(\frac{x}{6}\)
Solution:
Here, \(\frac{x}{2}\) + \(\frac{x}{6}\)
= \(\frac{3x + x}{6}\)
= \(\frac{4x}{6}\)
= \(\frac{2x}{3}\) ans.
Subtract: \(\frac{3a}{x}\) - \(\frac{2a}{5x}\)
Solution:
Here, \(\frac{3a}{x}\) - \(\frac{2a}{5x}\)
= \(\frac{5×3a - 2a}{5x}\)
= \(\frac{15a - 2a}{5x}\)
= \(\frac{13a}{5x}\)
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