wy
Lv 7
wy 發問於 科學及數學數學 · 5 年前

Maths Equation?

Is the solution to the equation (x^2 - 9) + (2x + 5) - 4 = 0 is also the solution to the equation |x^2 - 9| + |2x + 5| - 4 = 0?

If not, why not? Please explain.

2 個解答

評分
  • 5 年前

    The answer is "No".

    As the solution to the equation (x² - 9) + (2x + 5) - 4 = 0 is -4 or 2.

    But, the solution to the equation |x² - 9| + |2x + 5| - 4 = 0 is (1 - √19).

    They have different solution(s).

  • 5 年前

    Sol

    (x^2-9)+(2x+5)-4=0

    x^2+2x-8=0

    (x-2)(x+4)=0

    x=2 or x=-4

    when x=2

    |x^2-9|+|2x+5|-4=|4-9|+|4+5|-4=5+9-4=10<>0

    So

    x=2 is not the equation of |x^2-9|+|2x + 5|-4=0

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