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If X and Y are 2 × 2 matrices, then solve the following matrix equations for X and Y. 2X + 3Y = [2340], 3Y + 2Y = [-221-5]

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Question

If X and Y are 2 × 2 matrices, then solve the following matrix equations for X and Y.

2X + 3Y = `[(2, 3),(4, 0)]`, 3Y + 2Y = `[(-2, 2),(1, -5)]`

Sum
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Solution

Given that,

2X + 3Y = `[(2, 3),(4, 0)]`   ......(1)

3Y + 2Y = `[(-2, 2),(1, -5)]`   ......(2)

Multiplying equation (1) by 3 and equaion (2) by 2, we get,

3[2X + 3Y] = `3[(2, 3),(4, 0)]`

⇒ 6X + 9Y = `[(6, 9),(12, 0)]`  ....(3)

2[3X + 2Y] = `2[(-2, 2),(1, -5)]`

⇒ 6X + 4Y = `[(-4, 4),(2, -10)]`  .....(4)

On subtracting eq. (4) from eq. (3) we get

5Y = `[(6 + 4, 9 - 4),(12 - 2, 0 + 10)]`

5Y = `[(10, 5),(10, 10)]`

⇒ Y = `[(2, 1),(2, 2)]` 

Now, putting the value of Y in equation (1) we get,

`2"X" + 3 [(2, 1),(2, 2)] = [(2, 3),(4, 0)]`

⇒ `2"X" + [(6, 3),(6, 60)] = [(2, 3),(4, 0)]`

⇒ 2X = `[(2, 3),(4, 0)] - [(6, 3),(6, 6)]`

⇒ 2X = `[(2 - 6, 3 - 3),(4 - 6, 0 - 6)]`

⇒ 2X = `[(-4,0),(-2, -6)]`

⇒  = `1/2 [(-4, 0),(-2, -6)]`

⇒ X = `[(-2, 0),(-1, -3)]`

Hence, X = `[(-2, 0),(-1, -3)]` and Y = `[(2, 1),(2, 2)]`

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Chapter 3: Matrices - Exercise [Page 55]

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NCERT Exemplar Mathematics Exemplar [English] Class 12
Chapter 3 Matrices
Exercise | Q 19 | Page 55

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