## Book: RS Aggarwal - Mathematics

#### Subject: Maths - Class 10th

##### Q. No. 55 of Exercise 10A

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55
##### Solve each of the following quadratic equations:

taking LCM

x2 + 4x - 5 = 7 cross multiplying

x2 + 4x - 12 = 0

Using the splitting middle term - the middle term of the general equation is divided in two such values that:

Product = a.c

For the given equation a = 1 b = 4 c = - 12

= 1. - 12 = - 12

And either of their sum or difference = b

= 4

Thus the two terms are 6 and - 2

Difference = 6 - 2 = 4

Product = 6. - 2 = - 12

x2 + 4x - 12 = 0

x2 + 6x - 2x - 12 = 0

x(x + 6) - 2(x + 6) = 0

(x + 6)(x - 2) = 0

(x + 6) = 0 or (x - 2) = 0

x = - 6 or x = 2

Hence the roots of equation are - 6 or 2.

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