(c) (3x2 + 4x – 7) and (2x2 – 5x + 3
Let the two expressions be A and B.
Then, A + B = 5x2 – x – 4 .......…(i) A – B = x2 + 9x – 10 …(ii)
Adding eqn (i) and (ii), we get
2A = (5x2 + x2 ) + (–x + 9x) + (–4 – 10)
= 6x2 + 8x –14
\(\Rightarrow\)A = 3x2 + 4x – 7
\(\therefore\) From (i), B = (5x2 – x – 4) – A
= (5x2 – x – 4) – (3x2 + 4x – 7)
= 2x2 – 5x + 3