Question

Find the errors and correct the following mathematical sentence:

(3a + 4b)(a – b)= 3a² – 4a²

Answer 1

(3a + 4b)(a – b) = 3a² – 4a² 

3a(a – b) + 4b(a – b) = 3a² – 4a² 

3a² – 3ab + 4ab – 4b² = – a² 

3a² + ab – 4b² ≠ a²   

∴ The given sentence is wrong. 

Correct sentence is (3a + 4b) (a – b) = 3a² + ab – 4b²