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Solution


Q.

Assertion (A): 9x² - 3x - 20 = 0 ⇒ (3x - 5)(3x + 4) = 0.The roots are calculated by splitting the middle term.

Reason (R): To factorise ax² + bx + c = 0, we write in the form ax² + b₁x + b₂x + c = 0  such that b₁ + b₂ = b and b₁b₂ = ac.
1 Both A and R are true, and R is the correct explanation of A.
 
2 Both A and R are true, but R is not the correct explanation of A.  
3 A is true, but R is false.  
4 A is false, but R is true.  

Ans.

(1)

We have, 9x² - 3x - 20 = 0
⇒ 9x² - 15x + 12x - 20 = 0 ⇒ 3x(3x - 5) + 4(3x - 5) = 0
⇒ (3x - 5)(3x + 4) = 0
Hence, both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).