Question

By using identities, find
(5x-4 y)² + (5x + 4y)²
3marks question plz step by step​

Answer 1

(a+b)²⁼a²+b²+2ab

(5x-4y)²=(5x)²+(4y)²-2(5x)(4y)

(25x+16y-40xy)

(5x+4y)² = (5x)²+ (4y)²+2(5x)(4y)

25x²+16y²+40xy

25x²+16y²-40xy+25x²+16y²+40xy

50x²+32y²

Answer 2

$\huge\star\bold\blue{Answer}\huge\star$

Solution ⤵

Step 1 > use ( a - b) ² = a² - 2ab + b²

25 x² - 40xy + 16 y² + (5x + 4y)² Step 2> use (a + b)² = a² + 2ab + b²

25 x² - 40xy + 16y² + 25x² + 40xy + 16y²

Now the Equation is

$25 \: x {}^{2} - \: 16y {}^{2} + 25 \: x {}^{2} + \: 16y {}^{2}$

step 3> (Collect like terms)

50x² + 16 y² + 16 y²

Answer : 50 x² + 32 y²

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