| Thrice the square of a natural number decreased by four times the number is equal to 50 more than the number. The number is |
A) 4
B) 5
C) 10
D) 6
Correct Answer: B
Solution :
| Let the number be x. |
| Then, \[3{{x}^{2}}-4x=x+50\] |
| \[\Rightarrow \]\[3{{x}^{2}}-5x-50=0\] |
| \[\Rightarrow \]\[3{{x}^{2}}-15x+10x-50=0\] |
| \[\Rightarrow \]\[3x\,\,(x-5)-10\,\,(x-5)=0\] |
| \[\Rightarrow \] \[(3x-10)(x-5)=0\] |
| \[\Rightarrow \] \[x=\frac{10}{3},5\] |
| But the number is natural number |
| \[\therefore \] \[x=5\] |
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