Getal & Ruimte (12e editie) - vwo wiskunde B

'Wortelvergelijkingen'.

3 vwo 5.6 Wortelvergelijkingen

Wortelvergelijkingen (1)

opgave 1

Los exact op.

3p

\(5 + 2 \sqrt{x} = 9\)

Wortel (1)
008o - Wortelvergelijkingen - basis - 1ms - dynamic variables

○

(Isoleren)
\(2 \sqrt{x} = 4\)

1p

○

(Kwadrateren)
\((2 \sqrt{x})^{2} = 4^{2}\)
\(4 x = 16\)
\(x = 4\)

1p

○

(Controleren)
\(x = 4\) voldoet.

1p

vwo wiskunde B 4.3 Regels voor het oplossen van vergelijkingen

Wortelvergelijkingen (4)

opgave 1

Los exact op.

3p

a

\(x = \sqrt{-4 x + 12}\)

Wortel (2)
008n - Wortelvergelijkingen - basis - 0ms - dynamic variables

a

(Kwadrateren)
\(x^{2} = -4 x + 12\)

1p

○

(Oplossen)
\(x^{2} + 4 x - 12 = 0\)
\((x + 6) (x - 2) = 0\)
\(x = -6 ∨ x = 2\)

1p

○

(Controleren)
\(x = -6\) voldoet niet, \(x = 2\) voldoet.

1p

4p

b

\(6 x + 2 \sqrt{x} = 8\)

Wortel (4)
008p - Wortelvergelijkingen - basis - 4ms - dynamic variables

b

(Isoleren)
\(6 x - 8 = -2 \sqrt{x}\)

1p

○

(Kwadrateren)
\((6 x - 8)^{2} = (-2 \sqrt{x})^{2}\)
\(36 x^{2} - 96 x + 64 = 4 x\)

1p

○

(Oplossen)
\(36 x^{2} - 100 x + 64 = 0\)
\(9 x^{2} - 25 x + 16 = 0\)
\(D = (-25)^{2} - 4 ⋅ 9 ⋅ 16 = 49\)
\(x = {25 - \sqrt{49} \over 2 ⋅ 9} ∨ x = {25 + \sqrt{49} \over 2 ⋅ 9}\)
\(x = 1 ∨ x = 1\frac{7}{9}\)

1p

○

(Controleren)
\(x = 1\) voldoet, \(x = 1\frac{7}{9}\) voldoet niet.

1p

4p

c

\(x = \sqrt{3 x + 60} - 2\)

Wortel (3)
008q - Wortelvergelijkingen - basis - 0ms - dynamic variables

c

(Isoleren)
\(x + 2 = \sqrt{3 x + 60}\)

1p

○

(Kwadrateren)
\((x + 2)^{2} = (\sqrt{3 x + 60})^{2}\)
\(x^{2} + 4 x + 4 = 3 x + 60\)

1p

○

(Oplossen)
\(x^{2} + x - 56 = 0\)
\((x + 8) (x - 7) = 0\)
\(x = -8 ∨ x = 7\)

1p

○

(Controleren)
\(x = 7\) voldoet, \(x = -8\) voldoet niet.

1p

4p

d

\(4 x - 3 \sqrt{2 x - 2} = 9\)

Wortel (5)
008r - Wortelvergelijkingen - basis - 594ms - dynamic variables

d

(Isoleren)
\(4 x - 9 = 3 \sqrt{2 x - 2}\)

1p

○

(Kwadrateren)
\((4 x - 9)^{2} = (3 \sqrt{2 x - 2})^{2}\)
\(16 x^{2} - 72 x + 81 = 9 ⋅ (2 x - 2)\)
\(16 x^{2} - 72 x + 81 = 18 x - 18\)

1p

○

(Oplossen)
\(16 x^{2} - 90 x + 99 = 0\)
\(D = (-90)^{2} - 4 ⋅ 16 ⋅ 99 = 1\,764\)
\(x = {90 - \sqrt{1\,764} \over 2 ⋅ 16} ∨ x = {90 + \sqrt{1\,764} \over 2 ⋅ 16}\)
\(x = 1\frac{1}{2} ∨ x = 4\frac{1}{8}\)

1p

○

(Controleren)
\(x = 1\frac{1}{2}\) voldoet niet, \(x = 4\frac{1}{8}\) voldoet.

1p

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