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ESO Y4A · Mathematics
Equations · Equations and inequalities

Other types of equations

Not all equations have $x$ appearing plainly as a first- or second-degree term. Sometimes it is in a denominator, inside a root, or it only appears raised to the powers of 2 and 4. All three types can be solved with a trick that turns them into an equation you already know how to solve, and all three share a golden rule: always check your answers.

Before you start, make sure you know: Quadratic equations (3rd ESO)
Before you start, make sure you know: Special products (notable identities) (2nd ESO)

Rational equations

Rational equation with algebraic fractions and a warning sign highlighting that x cannot equal 1 or -3 because they would make the denominators zero. x + 2 x − 1 = x x + 3 x cannot be 1 or −3: they would make a denominator zero (division by 0 does not exist)
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Solve the following rational equation, paying attention to possible extraneous solutions that make the denominators zero: $\frac{x+2}{x-1} = \frac{x}{x+3}$

Solve the following rational equation, paying attention to possible extraneous solutions that make the denominators zero:

$\frac{x+2}{x-1} = \frac{x}{x+3}$

Solve
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A cyclist travels a distance of $60\text{ km}$ at a constant speed $v$. If they had ridden $5\text{ km/h}$ faster, it would have taken them $1$ hour less to complete the…

A cyclist travels a distance of $60\text{ km}$ at a constant speed $v$. If they had ridden $5\text{ km/h}$ faster, it would have taken them $1$ hour less to complete the same journey. Knowing that the time taken is $t = \frac{d}{v}$, set up a rational equation and determine the initial speed of the cyclist.

Solve

Irrational equations

Diagram of the method for solving an irrational equation: isolate the root on one side, square both sides and always check the solutions in the original equation. 2x + 5 = x + 3 ( )² 2x+5 = (x+3)²
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Find the value or values of $x$ that satisfy the following radical equation. Remember to check the validity of the solutions obtained: $\sqrt{2x+5} - 3 = x$

Find the value or values of $x$ that satisfy the following radical equation. Remember to check the validity of the solutions obtained:

$\sqrt{2x+5} - 3 = x$

Solve
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Isolate the radical, square both sides and solve the irrational equation. Check whether the solutions found are valid: $\sqrt{x^2+5x+1} = x+2$

Isolate the radical, square both sides and solve the irrational equation. Check whether the solutions found are valid:

$\sqrt{x^2+5x+1} = x+2$

Solve

Two radicals: isolate and repeat

Flowchart of the method for solving equations with two radicals: isolate one root, square both sides and repeat if another root remains. isolate a root square it ² root left?repeat

If there are two roots, you isolate one, square both sides, and if another root remains you repeat the process.

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Solve the following irrational equation involving two radicals. Isolate one of them, square both sides, and repeat the process if necessary. Do not forget to check the…

Solve the following irrational equation involving two radicals. Isolate one of them, square both sides, and repeat the process if necessary. Do not forget to check the validity of your results in the original equation:

$\sqrt{x+4} + \sqrt{x-1} = 5$

Solve

Biquadratic equations

Diagram of the process for solving biquadratic equations by the substitution t = x², solving the quadratic equation and undoing the substitution with x = ±√t. x⁴ − 13x² + 36 t = x² t² − 13t + 36 x = ±√t ±2, ±3
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Solve the following biquadratic equation, finding all its real solutions: $x^4 - 13x^2 + 36 = 0$

Solve the following biquadratic equation, finding all its real solutions:

$x^4 - 13x^2 + 36 = 0$

Solve
Practice★☆☆Not started
Solve the following incomplete biquadratic equation by taking out a common factor: $2x^4 - 32x^2 = 0$

Solve the following incomplete biquadratic equation by taking out a common factor:

$2x^4 - 32x^2 = 0$

Solve

Summary

See all the exercises in this section