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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 8: Phân tích các đa thức sau thành nhân tử x^2+7x-12

Toán Lớp 8: Phân tích các đa thức sau thành nhân tử x^2+7x-12

Comments ( 2 )

  1. Giải đáp:
     x^2 + 7x – 12
    = x^2 + 2.x . 7/2 + (7/2)^2 – (7/2)^2 – 12
    = (x + 7/2)^2 – 97/4
    = (x + 7/2)^2 – ($\dfrac{\sqrt{97}}{2}$)^2
    = (x + 7/2 + $\dfrac{\sqrt{97}}{2}$)(x + 7/2 – $\dfrac{\sqrt{97}}{2}$)

  2. $x^2+7x-12$
    $=x^2+2x.\dfrac{7}{2}+\dfrac{49}{4}-\dfrac{97}{4}$
    $=\bigg(x+\dfrac{7}{2}\bigg)^2-\bigg(\dfrac{\sqrt[]{97}}{2}\bigg)^2$
    $=\bigg(x+\dfrac{7}{2}-\dfrac{\sqrt[]{97}}{2}\bigg).\bigg(x+\dfrac{7}{2}+\dfrac{\sqrt[]{97}}{2}\bigg)$

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222-9+11+12:2*14+14 = ? ( )

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