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Evaluate (2x-3y+5)^(3)....

Evaluate `(2x-3y+5)^(3)`.

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To evaluate the expression \((2x - 3y + 5)^3\), we can use the formula for the cube of a binomial. However, since we have three terms, we will treat \(2x - 3y\) as one term (let's call it \(a\)) and \(5\) as another term (let's call it \(b\)). ### Step-by-step Solution: 1. **Identify the terms**: Let \(a = 2x - 3y\) and \(b = 5\). 2. **Use the formula for the cube of a sum**: The formula for \((a + b)^3\) is: \[ a^3 + b^3 + 3a^2b + 3ab^2 \] 3. **Calculate \(a^3\)**: \[ a^3 = (2x - 3y)^3 \] Using the binomial expansion: \[ (p - q)^3 = p^3 - 3p^2q + 3pq^2 - q^3 \] Here, \(p = 2x\) and \(q = 3y\): \[ = (2x)^3 - 3(2x)^2(3y) + 3(2x)(3y)^2 - (3y)^3 \] \[ = 8x^3 - 3 \cdot 4x^2 \cdot 3y + 3 \cdot 2x \cdot 9y^2 - 27y^3 \] \[ = 8x^3 - 36x^2y + 54xy^2 - 27y^3 \] 4. **Calculate \(b^3\)**: \[ b^3 = 5^3 = 125 \] 5. **Calculate \(3a^2b\)**: \[ 3a^2b = 3(2x - 3y)^2 \cdot 5 \] First, calculate \((2x - 3y)^2\): \[ = (2x)^2 - 2(2x)(3y) + (3y)^2 = 4x^2 - 12xy + 9y^2 \] Now multiply by \(5\): \[ 3(4x^2 - 12xy + 9y^2) \cdot 5 = 15(4x^2 - 12xy + 9y^2) = 60x^2 - 180xy + 135y^2 \] 6. **Calculate \(3ab^2\)**: \[ 3ab^2 = 3(2x - 3y)(5^2) = 3(2x - 3y) \cdot 25 = 75(2x - 3y) = 150x - 225y \] 7. **Combine all the terms**: Now, we combine all the results: \[ (2x - 3y + 5)^3 = a^3 + b^3 + 3a^2b + 3ab^2 \] \[ = (8x^3 - 36x^2y + 54xy^2 - 27y^3) + 125 + (60x^2 - 180xy + 135y^2) + (150x - 225y) \] 8. **Combine like terms**: \[ = 8x^3 + (60x^2 - 36x^2y) + (150x - 180xy + 54xy^2 + 135y^2) - 27y^3 + 125 \] \[ = 8x^3 - 27y^3 + 60x^2 - 36xy + 54xy^2 + 150x - 225y + 125 \] ### Final Answer: \[ (2x - 3y + 5)^3 = 8x^3 - 27y^3 + 60x^2 - 36xy + 54xy^2 + 150x - 225y + 125 \]
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NAGEEN PRAKASHAN ENGLISH-POLYNOMIALS-Exercise 2 E
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  2. Expand : (i) (3a-5b)^(2) " " (ii) (a+(1)/(a))^(2) " " (iii) (2x-(...

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  3. Expand : (i) (a+b-c)^(2) " " (ii) (a-2b-5c)^(2) " " (iii) (3a-2b...

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  4. Evaluate using formula : (i) (188)^(2) " " (ii) (9.4)^(2) " " (i...

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  5. (i) If a^(2)+b^(2)+c^(2)=20 " and" a+b+c=0, " find " ab+bc+ac. (ii) ...

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  6. Expand : (i) (2x+3y)^(3) " " (ii) (5y-3x)^(3) " " (iii) (2a+3b)...

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  7. Evaluate (2x-3y+5)^(3).

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  8. If a+2b=5, then show that a^(3)+8b^(3)+30ab=125.

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  9. If 2x-3y=10 and xy=16, find the value of 8x^(3)-27y^(3).

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  10. Evaluate : (i) (98)^(3) " " (ii) (598)^(3) " " (iii) (1003)^(3)

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  11. Factorise : 4a^(2)+9b^(2)+16c^(2)+12ab-24bc-16ca

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  12. Verify : (i) x^3+y^3=(x+y)(x^2-x y+y^2) (ii) x^3-y^3=(x-y)...

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  13. Factorise : (i) 9a^(3)-27b^(3) " " (ii) a^(3)-343 " " (iii) a^(...

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  14. Find the product : (i) (x+3)(x^(2)-3x+9) " " (ii) (7+5b)(49-35b+2...

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  15. Factorise : (i) a^(3)+27b^(3)+8c^(3)-18abc " " (ii) 2sqrt(2)a^(3)...

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  16. Find the product : (i) (a+2b+4c)(a^(2)+4b^(2)+16c^(2)-2ab-8bc-4ca) ...

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  17. Factorise : (i) (x-y)^(3)+(y-z)^(3)+(z-x)^(3) (ii) (x-2y)^(3)+(2y-...

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  18. Without actually calculating the cube find the value of the following ...

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  19. Verify that x^3+y^3+z^3-3xyz=1/2(x+y+z)[(x-y)^2+(y-z)^2+(z-x)^2]

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  20. If x+y+z=0show that x^3+y^3+z^3=3x y z.

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