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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