Math Problem Statement

laske lasku

Ratkaise yhtälöt: i) x² + 5x - 14 = 0, ii) x² + 8x + 16 = 0, iii) -4x² - 5x = 0

Solution

The image shows a mathematical task involving solving three quadratic equations. Let's solve them step by step:


i) x2+5x14=0x^2 + 5x - 14 = 0

To solve this quadratic equation, we use the quadratic formula: x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} Here:

  • a=1a = 1,
  • b=5b = 5,
  • c=14c = -14.

Substitute these values into the formula: x=5±524(1)(14)2(1)x = \frac{-5 \pm \sqrt{5^2 - 4(1)(-14)}}{2(1)} x=5±25+562x = \frac{-5 \pm \sqrt{25 + 56}}{2} x=5±812x = \frac{-5 \pm \sqrt{81}}{2} x=5±92x = \frac{-5 \pm 9}{2}

Now, calculate the two solutions:

  1. x1=5+92=42=2x_1 = \frac{-5 + 9}{2} = \frac{4}{2} = 2,
  2. x2=592=142=7x_2 = \frac{-5 - 9}{2} = \frac{-14}{2} = -7.

Solution for i: x=2x = 2 or x=7x = -7.


ii) x2+8x+16=0x^2 + 8x + 16 = 0

This is a perfect square trinomial: x2+8x+16=(x+4)2=0x^2 + 8x + 16 = (x + 4)^2 = 0 Thus: x+4=0    x=4x + 4 = 0 \implies x = -4

Solution for ii: x=4x = -4 (repeated root).


iii) 4x25x=0-4x^2 - 5x = 0

First, factor out x-x: 4x25x=0    x(4x+5)=0-4x^2 - 5x = 0 \implies -x(4x + 5) = 0 This gives two solutions:

  1. x=0    x=0-x = 0 \implies x = 0,
  2. 4x+5=0    x=544x + 5 = 0 \implies x = -\frac{5}{4}.

Solution for iii: x=0x = 0 or x=54x = -\frac{5}{4}.


Final Answers:

i) x=2x = 2 or x=7x = -7
ii) x=4x = -4
iii) x=0x = 0 or x=54x = -\frac{5}{4}

Let me know if you'd like further clarification or details!


Follow-up Questions:

  1. What is the quadratic formula, and why is it used?
  2. How can you recognize a perfect square trinomial?
  3. How do you factorize quadratic equations efficiently?
  4. What is the significance of a "repeated root"?
  5. When should you factor out terms in an equation?

Tip:

Always check for simple factoring options first before using the quadratic formula—it can save time!

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations

Formulas

Quadratic formula: x = (-b ± √(b² - 4ac)) / 2a

Theorems

Quadratic Formula Theorem

Suitable Grade Level

Grades 7-9