Question

What is the number of real solutions of the equation x2 - 7|x| - 18 = 0?
2
4
3
1

Answer 1

2 real solutions the equations will have

Answer 2

x²-7|x|-18=0 can also be written as |x|²-7|x|-18=0

Now the above equation can be factorise as

|x|²+2|x|-9|x|-18=0

Thus, |x|( |x|+2 ) -9(|x|+2) =0

(|x|-9)(|x|+2)=0

|x|=9 therefore x= 9,-9

and |x|= -2 which is not possible since modulus function always gives positive output

thus this equation has two real solutions

which are x={ 9,-9}