If A = ((1,-1),(2-1)) and B = ((a,1),(b,-1)) and ​

Question

If A = \( \begin{pmatrix} 1&-1 \\ 2 &-1 \end{pmatrix}\) and B = \( \begin{pmatrix} a&1 \\ b &-1 \end{pmatrix}\)and 

(A + B)² = (A² + B²) then 

A. a = 2, b = -3 

B. a = -2, b = 3 

C. a = 1, b = 4 

D. none of these

Answer 1

A = \( \begin{pmatrix} 1&-1 \\ 2 &-1 \end{pmatrix}\)B = \( \begin{pmatrix} a&1 \\ b &-1 \end{pmatrix}\)

By comparison, 

a - 1 = 0 

a = 1 

b = 4