MCQ
Square of $9x - 7xy$ is:
- A$81x^2 + 49x^2y^2$
- B$81x^2 - 49x^2y^2$
- ✓$81x^2 + 49x^2y^2 - 126x^2y$
- D$81x^2+ 49x^2y^2 - 63x^2y$
✓
Answer
Correct option: C.
$81x^2 + 49x^2y^2 - 126x^2y$
C. $81x^2 + 49x^2y^2 - 126x^2y$
Solution:
Square of $(9x - 7xy) = (9x- 7x)^2$
Comparing with $(a - b)^2$
we get $a = 9x$ and $b = 7xy$
$(9x - 7xy)^2 = (9x)^2 - 2.9x. 7xy + (7xy)^2$
$= 81x^2 - 126x^2y + 49x^2y^2$
$= 81x^2+ 49x^2y^2 - 126x^2y$
Solution:
Square of $(9x - 7xy) = (9x- 7x)^2$
Comparing with $(a - b)^2$
we get $a = 9x$ and $b = 7xy$
$(9x - 7xy)^2 = (9x)^2 - 2.9x. 7xy + (7xy)^2$
$= 81x^2 - 126x^2y + 49x^2y^2$
$= 81x^2+ 49x^2y^2 - 126x^2y$
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