Question

Alan thinks of a number. He squares it, then takes away 5, next multiplies it by 4, takes away 7, divides it by 3 and finally adds 6. His answer is 9. What number did Alan start with?

Answer 1

Answer: $\pm3$

Step-by-step explanation:

$[(4(x^{2} -5)-7)/3]+6=9$

$((4x^{2} -20)-7)/3=9-6$

$4x^{2} -27=3*3$

$4x^{2} =9+27$

$x^{2}=36/4=9$

$x=\sqrt{9} =\pm3$

$x = 3$