MCQ
Square of $3x - 4y$ is:
- A$9x^2 - 16y^2$
- B$6x^2 - 8y^2$
- C$9x^2 + 16y^2+ 24xy$
- ✓$9x^2 + 16y^2 - 24xy$
✓
Answer
Correct option: D.
$9x^2 + 16y^2 - 24xy$
D. $9x^2 + 16y^2 - 24xy$
Solution:
Square of $(3x - 4y)$ will be $(3x - 4y)^2$
comparing $(3x - 4y)^2$ with $(a - b)^2$
We get $a = 3x$ and $b = 4y$
now, using identity, $(a - b)^2 = a^2 - 2ab + b^2$
$(3x - 4y)^2 = (3x)^2 - 2.3x.4y + (4y)^2$
$= 9x^2 + 16y^2 - 24xy$
Solution:
Square of $(3x - 4y)$ will be $(3x - 4y)^2$
comparing $(3x - 4y)^2$ with $(a - b)^2$
We get $a = 3x$ and $b = 4y$
now, using identity, $(a - b)^2 = a^2 - 2ab + b^2$
$(3x - 4y)^2 = (3x)^2 - 2.3x.4y + (4y)^2$
$= 9x^2 + 16y^2 - 24xy$
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