Learn on PengiOpenstax Elementary Algebra 2EChapter 9: Roots and Radicals

Lesson 9.3: Add and Subtract Square Roots

This lesson from OpenStax Elementary Algebra 2E teaches students how to add and subtract like square roots by combining coefficients when radicands match, just as they would combine like terms in algebra. Students also learn to simplify square roots using the Product and Quotient Properties before adding or subtracting expressions with unlike radicands. Real-world applications, such as finding garden dimensions and calculating falling-object times, reinforce these radical arithmetic skills.

Section 1

📘 Add and Subtract Square Roots

New Concept

Master adding and subtracting square roots by treating them like algebraic terms. You'll combine like square roots—those with the same radicand—and simplify others, like 48\sqrt{48}, to find hidden like terms before performing the operation.

What’s next

Get ready to apply this concept! Next up are interactive examples and practice cards that break down simplifying and combining radicals step-by-step.

Section 2

Like Square Roots

Property

Square roots with the same radicand are called like square roots.
We add and subtract like square roots in the same way we add and subtract like terms.
Trying to add square roots with different radicands is like trying to add unlike terms.

Examples

  • 53+23=735\sqrt{3} + 2\sqrt{3} = 7\sqrt{3}
  • 8x−3x=5x8\sqrt{x} - 3\sqrt{x} = 5\sqrt{x}

Section 3

Add and Subtract Like Square Roots

Property

To add or subtract like square roots, add or subtract their coefficients.
The radicand remains the same.
This process is similar to combining like terms in algebra, such as 3x+8x=11x3x + 8x = 11x.
Similarly, 3x+8x=11x3\sqrt{x} + 8\sqrt{x} = 11\sqrt{x}.

Examples

  • 411+511=(4+5)11=9114\sqrt{11} + 5\sqrt{11} = (4+5)\sqrt{11} = 9\sqrt{11}
  • 9m−12m=(9−12)m=−3m9\sqrt{m} - 12\sqrt{m} = (9-12)\sqrt{m} = -3\sqrt{m}

Section 4

Simplify before combining

Property

Sometimes when we have to add or subtract square roots that do not appear to have like radicals, we find like radicals after simplifying the square roots.
Always simplify square roots by removing the largest perfect-square factor.

Examples

  • 12+33=4â‹…3+33=23+33=53\sqrt{12} + 3\sqrt{3} = \sqrt{4 \cdot 3} + 3\sqrt{3} = 2\sqrt{3} + 3\sqrt{3} = 5\sqrt{3}
  • 50−18=25â‹…2−9â‹…2=52−32=22\sqrt{50} - \sqrt{18} = \sqrt{25 \cdot 2} - \sqrt{9 \cdot 2} = 5\sqrt{2} - 3\sqrt{2} = 2\sqrt{2}

Section 5

Combining roots with variables

Property

When radicals contain variables, they are considered like radicals if the radicand (both the constant and variable parts) is identical after simplification.
First, simplify each radical by removing all perfect-square factors, then combine the coefficients of any like radicals.

Examples

  • 27y5−12y5=9y4â‹…3y−4y4â‹…3y=3y23y−2y23y=y23y\sqrt{27y^5} - \sqrt{12y^5} = \sqrt{9y^4 \cdot 3y} - \sqrt{4y^4 \cdot 3y} = 3y^2\sqrt{3y} - 2y^2\sqrt{3y} = y^2\sqrt{3y}
  • 245x2+x80=29x2â‹…5+x16â‹…5=2(3x)5+x(4)5=6x5+4x5=10x52\sqrt{45x^2} + x\sqrt{80} = 2\sqrt{9x^2 \cdot 5} + x\sqrt{16 \cdot 5} = 2(3x)\sqrt{5} + x(4)\sqrt{5} = 6x\sqrt{5} + 4x\sqrt{5} = 10x\sqrt{5}

Book overview

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Continue this chapter

Chapter 9: Roots and Radicals

  1. Lesson 1

    Lesson 9.1: Simplify and Use Square Roots

  2. Lesson 2

    Lesson 9.2: Simplify Square Roots

  3. Lesson 3Current

    Lesson 9.3: Add and Subtract Square Roots

  4. Lesson 4

    Lesson 9.4: Multiply Square Roots

  5. Lesson 5

    Lesson 9.5: Divide Square Roots

  6. Lesson 6

    Lesson 9.6: Solve Equations with Square Roots

  7. Lesson 7

    Lesson 9.7: Higher Roots

  8. Lesson 8

    Lesson 9.8: Rational Exponents

Lesson overview

Expand to review the lesson summary and core properties.

Expand

Section 1

📘 Add and Subtract Square Roots

New Concept

Master adding and subtracting square roots by treating them like algebraic terms. You'll combine like square roots—those with the same radicand—and simplify others, like 48\sqrt{48}, to find hidden like terms before performing the operation.

What’s next

Get ready to apply this concept! Next up are interactive examples and practice cards that break down simplifying and combining radicals step-by-step.

Section 2

Like Square Roots

Property

Square roots with the same radicand are called like square roots.
We add and subtract like square roots in the same way we add and subtract like terms.
Trying to add square roots with different radicands is like trying to add unlike terms.

Examples

  • 53+23=735\sqrt{3} + 2\sqrt{3} = 7\sqrt{3}
  • 8x−3x=5x8\sqrt{x} - 3\sqrt{x} = 5\sqrt{x}

Section 3

Add and Subtract Like Square Roots

Property

To add or subtract like square roots, add or subtract their coefficients.
The radicand remains the same.
This process is similar to combining like terms in algebra, such as 3x+8x=11x3x + 8x = 11x.
Similarly, 3x+8x=11x3\sqrt{x} + 8\sqrt{x} = 11\sqrt{x}.

Examples

  • 411+511=(4+5)11=9114\sqrt{11} + 5\sqrt{11} = (4+5)\sqrt{11} = 9\sqrt{11}
  • 9m−12m=(9−12)m=−3m9\sqrt{m} - 12\sqrt{m} = (9-12)\sqrt{m} = -3\sqrt{m}

Section 4

Simplify before combining

Property

Sometimes when we have to add or subtract square roots that do not appear to have like radicals, we find like radicals after simplifying the square roots.
Always simplify square roots by removing the largest perfect-square factor.

Examples

  • 12+33=4â‹…3+33=23+33=53\sqrt{12} + 3\sqrt{3} = \sqrt{4 \cdot 3} + 3\sqrt{3} = 2\sqrt{3} + 3\sqrt{3} = 5\sqrt{3}
  • 50−18=25â‹…2−9â‹…2=52−32=22\sqrt{50} - \sqrt{18} = \sqrt{25 \cdot 2} - \sqrt{9 \cdot 2} = 5\sqrt{2} - 3\sqrt{2} = 2\sqrt{2}

Section 5

Combining roots with variables

Property

When radicals contain variables, they are considered like radicals if the radicand (both the constant and variable parts) is identical after simplification.
First, simplify each radical by removing all perfect-square factors, then combine the coefficients of any like radicals.

Examples

  • 27y5−12y5=9y4â‹…3y−4y4â‹…3y=3y23y−2y23y=y23y\sqrt{27y^5} - \sqrt{12y^5} = \sqrt{9y^4 \cdot 3y} - \sqrt{4y^4 \cdot 3y} = 3y^2\sqrt{3y} - 2y^2\sqrt{3y} = y^2\sqrt{3y}
  • 245x2+x80=29x2â‹…5+x16â‹…5=2(3x)5+x(4)5=6x5+4x5=10x52\sqrt{45x^2} + x\sqrt{80} = 2\sqrt{9x^2 \cdot 5} + x\sqrt{16 \cdot 5} = 2(3x)\sqrt{5} + x(4)\sqrt{5} = 6x\sqrt{5} + 4x\sqrt{5} = 10x\sqrt{5}

Book overview

Jump across lessons in the current chapter without opening the full course modal.

Continue this chapter

Chapter 9: Roots and Radicals

  1. Lesson 1

    Lesson 9.1: Simplify and Use Square Roots

  2. Lesson 2

    Lesson 9.2: Simplify Square Roots

  3. Lesson 3Current

    Lesson 9.3: Add and Subtract Square Roots

  4. Lesson 4

    Lesson 9.4: Multiply Square Roots

  5. Lesson 5

    Lesson 9.5: Divide Square Roots

  6. Lesson 6

    Lesson 9.6: Solve Equations with Square Roots

  7. Lesson 7

    Lesson 9.7: Higher Roots

  8. Lesson 8

    Lesson 9.8: Rational Exponents