Math Problem Statement

6. Diketahui dua matriks A dan B sebagai berikut: A = [ [5, 7], [2, 9] ], B = [ [5, x], [2, y] ]. Jika 2A = B, tentukan: a) Nilai x dan y, b) Nilai 2x + y, c) Nilai 2x + 4y. 7. Diketahui matriks sebagai berikut: M = [ [q-4, -8, 2d-3], [b, 2c, -13] ], N = [ [3a, -8, 11], [2b-5, 3c+8, -13] ]. Jika M = N, tentukan: a) Nilai a, b, dan c, b) Nilai 2a + 3b + 9c.

Solution

From the image you've uploaded, there are two separate matrix equations given. Let's solve each one step-by-step:

Problem 6

Given matrices AA and BB as follows: A=[5729]andB=[5x2y]A = \begin{bmatrix} 5 & 7 \\ 2 & 9 \end{bmatrix} \quad \text{and} \quad B = \begin{bmatrix} 5 & x \\ 2 & y \end{bmatrix} It is stated that 2A=B2A = B.

To find this relation: 2A=2[5729]=[1014418]2A = 2 \begin{bmatrix} 5 & 7 \\ 2 & 9 \end{bmatrix} = \begin{bmatrix} 10 & 14 \\ 4 & 18 \end{bmatrix} Comparing this with BB, we set: [1014418]=[5x2y]\begin{bmatrix} 10 & 14 \\ 4 & 18 \end{bmatrix} = \begin{bmatrix} 5 & x \\ 2 & y \end{bmatrix} From here, we solve:

  • For xx, 14=x14 = x.
  • For yy, 18=y18 = y.

Additionally, calculate:

  • 2x+y2x + y
  • 2x+4y2x + 4y

Calculations:

  • 2x+y=2(14)+18=28+18=462x + y = 2(14) + 18 = 28 + 18 = 46
  • 2x+4y=2(14)+4(18)=28+72=1002x + 4y = 2(14) + 4(18) = 28 + 72 = 100

Problem 7

Given matrices MM and NN as: M=[q482d3b2c13]andN=[3a8112b53c+813]M = \begin{bmatrix} q-4 & -8 & 2d-3 \\ b & 2c & -13 \end{bmatrix} \quad \text{and} \quad N = \begin{bmatrix} 3a & -8 & -11 \\ 2b-5 & 3c+8 & -13 \end{bmatrix} It's given M=NM = N.

From this equality:

  1. q4=3aq-4 = 3a
  2. 2d3=112d-3 = -11 implies 2d=82d = -8 so d=4d = -4.
  3. b=2b5b = 2b - 5 implies b=5b = 5.
  4. 2c=3c+82c = 3c + 8 implies c=8c = -8.

Finally, find 2a+2b+9c2a + 2b + 9c:

  • 2a=23(q4)2a = \frac{2}{3}(q-4)
  • 2b=2×5=102b = 2 \times 5 = 10
  • 9c=9×(8)=729c = 9 \times (-8) = -72

Calculation:

  • 2a+2b+9c=23(q4)+10722a + 2b + 9c = \frac{2}{3}(q-4) + 10 - 72

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Math Problem Analysis

Mathematical Concepts

Matrix equations
Algebra

Formulas

Matrix multiplication
System of equations

Theorems

Equality of matrices
Basic matrix operations

Suitable Grade Level

Grades 10-12