MCQ
What must be subtracted from $3a^2 - 6ab - 3b^2 - 1$ to get $4a^2 - 7ab - 4b^2 + 1?$
- A$-a^2 + ab + b^3 - 2$
- ✓$-a^2 + ab + b^2 - 2$
- C$a^2 + ab + b^2 - 2$
- D$-a^2 + ab + b^3 - 2$
✓
Answer
Correct option: B.
$-a^2 + ab + b^2 - 2$
Let X be subtracted from $3a^2 - 6ab - 3b^2$ Then,
$3a^2 - 6ab - 3b^2 - 1 - X = 4a^2 - 7ab - 4b^2 + 1$
$x = 3a^2 - 6ab - 3b^2 - 1 -(4a^2 - 7ab - 4b^2 + 1)$
$x = 3a^2 - 6ab - 3b^2- 1 -4a^2 + 7ab + 4b^2 - 1$
$x = -a^2 + ab + b^2 - 2$
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