Question

simplify (5x-7y)3+(5x+7y)3

Answer 1

Answer:

30X

Step-by-step explanation:

(5X-7Y)3 + (5X+7Y)3

= 15X-21Y+15X+21Y

=30X

Answer 2

Answer:

Let us expand the given expression:

(5x – 7y)3 + (5x + 7y)3 = [(5x)3 -{3 ×(5x)2 × (7y)} +{3 ×(5x)×(7y)2} -(7y)3] + [(5x)3 +{3 ×(5x)2 ×(7y)} +{3 ×(5x)×(7y)2} + (7y)3]

By using the formula,

(a + b)3 = a3 + 3a2b + 3ab2 + b3 and (a – b)3 = a3 – 3a2b + 3ab2 – b3

= [125x3 – {3 × 25x2 × 7y} + {3 × 5x × 49y2} – 343y3] + [125x3 + {3 × 25x2 × 7y} + {3 × 5x × 49y2} + 343y3]

= [125x3 – 525x2y + 735xy2 – 343y3] + [125x3 + 525x2y + 735xy2 + 343y3]

= 125x3 – 525x2y + 735xy2 – 343y3 + 125x3 + 525x2y + 735xy2 + 343y3

= 250x3 + 1470xy2

∴ (5x – 7y)3 + (5x + 7y)3 = 250x3 + 1470xy2