Getal & Ruimte (13e editie) - vwo wiskunde B

'Stelsels oplossen'.

vwo wiskunde B 4.1 Stelsels vergelijkingen

Stelsels oplossen (6)

opgave 1

Los exact op.

3p

a

\(\begin{cases}a-b=-5 \\ 3a-b=-6\end{cases}\)

Eliminatie (1)
003f - Stelsels oplossen - basis - dynamic variables

a

Aftrekken geeft \(-2a=1\text{,}\) dus \(a=-\frac{1}{2}\text{.}\)

1p

\(\begin{rcases}a-b=-5 \\ a=-\frac{1}{2}\end{rcases}\begin{matrix}-\frac{1}{2}-b=-5 \\ -b=-4\frac{1}{2} \\ b=4\frac{1}{2}\end{matrix}\)

1p

De oplossing is \((a, b)=(-\frac{1}{2}, 4\frac{1}{2})\text{.}\)

1p

4p

b

\(\begin{cases}x+3y=5 \\ 2x+2y=4\end{cases}\)

Eliminatie (2)
003g - Stelsels oplossen - basis - dynamic variables

b

\(\begin{cases}x+3y=5 \\ 2x+2y=4\end{cases}\) \(\begin{vmatrix}2 \\ 1\end{vmatrix}\) geeft \(\begin{cases}2x+6y=10 \\ 2x+2y=4\end{cases}\)

1p

Aftrekken geeft \(4y=6\text{,}\) dus \(y=1\frac{1}{2}\text{.}\)

1p

\(\begin{rcases}x+3y=5 \\ y=1\frac{1}{2}\end{rcases}\begin{matrix}x+3⋅1\frac{1}{2}=5 \\ x=\frac{1}{2}\end{matrix}\)

1p

De oplossing is \((x, y)=(\frac{1}{2}, 1\frac{1}{2})\text{.}\)

1p

4p

c

\(\begin{cases}2p-2q=-4 \\ 5p+3q=2\end{cases}\)

Eliminatie (3)
003h - Stelsels oplossen - basis - dynamic variables

c

\(\begin{cases}2p-2q=-4 \\ 5p+3q=2\end{cases}\) \(\begin{vmatrix}3 \\ 2\end{vmatrix}\) geeft \(\begin{cases}6p-6q=-12 \\ 10p+6q=4\end{cases}\)

1p

Optellen geeft \(16p=-8\text{,}\) dus \(p=-\frac{1}{2}\text{.}\)

1p

\(\begin{rcases}2p-2q=-4 \\ p=-\frac{1}{2}\end{rcases}\begin{matrix}2⋅-\frac{1}{2}-2q=-4 \\ -2q=-3 \\ q=1\frac{1}{2}\end{matrix}\)

1p

De oplossing is \((p, q)=(-\frac{1}{2}, 1\frac{1}{2})\text{.}\)

1p

4p

d

\(\begin{cases}y=5x-29 \\ y=2x-14\end{cases}\)

GelijkStellen
003i - Stelsels oplossen - basis

d

Gelijk stellen geeft \(5x-29=2x-14\)

1p

\(3x=15\) dus \(x=5\)

1p

\(\begin{rcases}y=5x-29 \\ x=5\end{rcases}\begin{matrix}y=5⋅5-29 \\ y=-4\end{matrix}\)

1p

De oplossing is \((x, y)=(5, -4)\text{.}\)

1p

opgave 2

Los exact op.

4p

a

\(\begin{cases}4x+2y=-20 \\ x=9y-24\end{cases}\)

Substitutie (1)
003j - Stelsels oplossen - basis - dynamic variables

a

Substitutie geeft \(4(9y-24)+2y=-20\)

1p

Haakjes wegwerken geeft
\(36y-96+2y=-20\)
\(38y=76\)
\(y=2\)

1p

\(\begin{rcases}x=9y-24 \\ y=2\end{rcases}\begin{matrix}x=9⋅2-24 \\ x=-6\end{matrix}\)

1p

De oplossing is \((x, y)=(-6, 2)\text{.}\)

1p

4p

b

\(\begin{cases}b=6a+4 \\ a=8b+15\end{cases}\)

Substitutie (2)
003k - Stelsels oplossen - basis - dynamic variables

b

Substitutie geeft \(b=6(8b+15)+4\)

1p

Haakjes wegwerken geeft
\(b=48b+90+4\)
\(-47b=94\)
\(b=-2\)

1p

\(\begin{rcases}a=8b+15 \\ b=-2\end{rcases}\begin{matrix}a=8⋅-2+15 \\ a=-1\end{matrix}\)

1p

De oplossing is \((a, b)=(-1, -2)\text{.}\)

1p

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