Question

(7q-2r)^3 find using identity

Please help me with this math question plz​

Answer 1

Question:-

➡ Expand (7q - 2r)³ using identity.

Answer:-

➡ Answer is = 343q³ - 8q³ - 294q²r + 84qr²

Solution:-

(7q - 2r)³

= (7q)³ - (2r)³ - 3×(7q)²×(2r) + 3×(7q)×(2r)²

= 343q³ - 8r³ - 3×49q²×2r + 3×7q×4r²

= 343q³ - 8q³ - 294q²r + 84qr²

Identity used:-

➡ (x - y)³ = x³ - y³ - 3x²y + 3xy²

Other identities:-

➡ (x + y)² = x² + 2xy + y²

➡ (x - y)² = x² - 2xy + y²

➡ x² - y² = (x + y)(x - y)

➡ (x + y)³ = x³ + y³ + 3x²y + 3xy²

Answer 2

Answer:

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