matrix algebra

[Sonal7]

I am confused about a Question that uses algebra to solve

I have done some workings but I am not sure how to derive the ans.

 

[Sonal7]

This is the answer but I am not sure fully clear on the steps. I think I have gone down the wrong way. I think SF just means the elements of the diagonals are both 15.

 

[Sonal7]

i have worked out that [MATH]b=-a[/MATH][MATH]a^2+ab=0[/MATH][MATH]a(a+b)=0[/MATH]since a is not equal to 0. a=-b.

I have already worked out the rest.
[MATH]2a+b^2=15[/MATH][MATH](b+3)(b-5)=0[/MATH]b is -3 or 5. if you sub into one of the equations its clear it is -3.
Sorry to waste your time.

 

[Deleted member 4993]

View attachment 21958

This is the answer but I am not sure fully clear on the steps. I think I have gone down the wrong way. I think SF just means the elements of the diagonals are both 15.

Your R²(1,1) is incorrect.