Grade 11 Mathematics
Grade 11 ยท Term 1Mathematics

Exponents & Surds

We extend Grade 10 exponent work to include equations with rational exponents and surds, and apply surd rationalization in more complex algebraic contexts.

Week 1

1.1 Rational Exponents & Equations with Surds

  • Simplify and solve equations with rational exponents
  • Solve equations involving surds (checking for extraneous roots)
  • Apply exponential laws to simplify complex expressions
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Real-World Connection

Equations with surds appear in structural engineering: the deflection of a beam involves square roots of variables. An extraneous solution would mean choosing a beam that collapses โ€” so checking every answer is not optional.

Property / Rule

Solving Exponential Equations

Write both sides with the same base, then equate exponents. If bases cannot be matched directly, use logarithms (introduced later).

af(x)=ag(x)โ‡’f(x)=g(x),a>0,โ€…โ€Šaโ‰ 1a^{f(x)} = a^{g(x)} \Rightarrow f(x) = g(x),\quad a>0,\; a\neq1

Property / Rule

Solving Surd Equations

Isolate the surd, then square both sides to eliminate the radical. ALWAYS substitute back to check for extraneous roots (introduced by squaring).

f(x)=g(x)โ‡’f(x)=g(x)2(check:ย g(x)โ‰ฅ0)\sqrt{f(x)}=g(x)\Rightarrow f(x)=g(x)^2\quad(\text{check: }g(x)\geq0)

โš ๏ธ Warning

Squaring both sides can introduce extraneous (false) solutions. For example, squaring x=โˆ’2\sqrt{x}=-2 gives x=4x=4, but 4=+2โ‰ โˆ’2\sqrt{4}=+2\neq-2. ALWAYS substitute back.

Worked Examples

Worked Example

Exponential equation

Problem

Solve: 4^{x-1} = 8

Worked Example

Surd equation

Problem

Solve:3xโˆ’2=xโˆ’2Solve: \sqrt{3x-2} = x-2
Activity โ€” 8 Questions

CAPS Cognitive Level Distribution

L1 ยท Knowledge2 Q
L2 ยท Routine Procedures2 Q
L3 ยท Complex Procedures2 Q
L4 ยท Problem Solving2 Q
1
L1 ยท Knowledge2 marks
Solve 23x=642^{3x}=64.
2
L1 ยท Knowledge2 marks
Simplify (x3yโˆ’2)2\left(\dfrac{x^3}{y^{-2}}\right)^2.
3
L2 ยท Routine Procedures4 marks
Solve 32xโˆ’4โ‹…3x+3=03^{2x}-4\cdot3^x+3=0.
4
L2 ยท Routine Procedures3 marks
Solve x+5=3\sqrt{x+5}=3.
5
L3 ยท Complex Procedures5 marks
Solve 2x+3โˆ’xโˆ’1=2\sqrt{2x+3}-\sqrt{x-1}=2.
6
L3 ยท Complex Procedures4 marks
Simplify 9n+1โˆ’32n32n+1\dfrac{9^{n+1}-3^{2n}}{3^{2n+1}}.
7
L4 ยท Problem Solving5 marks
If 2x+2โˆ’x=52^x+2^{-x}=5, find 4x+4โˆ’x4^x+4^{-x}.
8
L4 ยท Problem Solving6 marks
Solve x+x+9=9x+9โˆ’x\sqrt{x}+\sqrt{x+9}=\dfrac{9}{\sqrt{x+9}-\sqrt{x}}.
Exponents & Surds Grade 11 Maths CAPS Notes & Examples | MathSciBuddy