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Matrices · Question 30 of 106

Question 30

MediumOriginal question

If [2x−y31x+3y]=[53113]\begin{bmatrix} 2x - y & 3 \\ 1 & x + 3y \end{bmatrix} = \begin{bmatrix} 5 & 3 \\ 1 & 13 \end{bmatrix}, what are xx and yy?

Options for question 30

Show the answer and explanation
CorrectNot quiteAnswer D

Correct answer: D

Explanation

  1. Equal matrices have equal corresponding elements: 2x−y=52x - y = 5 and x+3y=13x + 3y = 13.

  2. From the first, y=2x−5y = 2x - 5; then x+6x−15=13x + 6x - 15 = 13, so x=4x = 4 and y=3y = 3.

Worth noting

x=3, y=4x = 3,\ y = 4 swaps the two; put the values back into 2x−y=52x - y = 5 to check.

Concept
Equality of matrices
Typical time
90 s
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The rule this testsEquality of matrices
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Ten questions from Matrices, at your own pace.

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Ten questions from Matrices, at your own pace.