The complex numbers zz and ww satisfy the following equations. 4z+5iw=74z + 5iw = 7
(1−i)z+8w=30(1 - i)z + 8w = 30
Find zz and ww, giving your answers in the form a+iba + ib where aa and bb are real numbers.

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Worked solution

1

1. Multiply the equations by suitable factors to align the coefficients of $z$.

Multiply the first equation by (1−i)(1 - i) and the second by 44:
4(1−i)z+5i(1−i)w=7(1−i)4(1 - i)z + 5i(1 - i)w = 7(1 - i)
4(1−i)z+32w=1204(1 - i)z + 32w = 120

2. Subtract the equations to eliminate $z$ and simplify the $w$ terms.

Subtract the first equation from the second:
32w−5i(1−i)w=120−7(1−i)32w - 5i(1 - i)w = 120 - 7(1 - i)
(32−5i+5i2)w=120−7+7i(32 - 5i + 5i^2)w = 120 - 7 + 7i
(32−5i−5)w=113+7i(32 - 5i - 5)w = 113 + 7i
(27−5i)w=113+7i(27 - 5i)w = 113 + 7i

3. Solve for $w$ by multiplying the numerator and denominator by the complex conjugate.

w=113+7i27−5iw = \frac{113 + 7i}{27 - 5i}
w=(113+7i)(27+5i)(27−5i)(27+5i)w = \frac{(113 + 7i)(27 + 5i)}{(27 - 5i)(27 + 5i)}
w=3051+565i+189i+35i2272+52w = \frac{3051 + 565i + 189i + 35i^2}{27^2 + 5^2}
w=3051−35+754i729+25w = \frac{3051 - 35 + 754i}{729 + 25}
w=3016+754i754w = \frac{3016 + 754i}{754}
w=4+iw = 4 + i

4. Substitute $w$ back into the first equation to find $z$.

4z+5i(4+i)=74z + 5i(4 + i) = 7
4z+20i+5i2=74z + 20i + 5i^2 = 7
4z+20i−5=74z + 20i - 5 = 7
4z=12−20i4z = 12 - 20i
z=3−5iz = 3 - 5i

Answer

z=3−5iz = 3 - 5i, w=4+iw = 4 + i

AI analysis — may contain mistakes.

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