Simplify (5z - 7y)2 + (7z + 5y)2 - 49z2
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 25z2 + 74y2.
(a - b)2 = a2 - 2ab + b2
(a + b)2 = a2 + 2ab + b2
Now, (5z - 7y)2 + (7z + 5y)2 - 49z2
= (25z2 - 70zy + 49y2) + (49z2 + 70zy + 25y2) - 49z2
= 25z2 - 70zy + 49y2 + 49z2 + 70zy + 25y2 - 49z2
= 25z2 + 74y2
Therefore, the required value is 25z2 + 74y2.