Question

Find the numbers such that the square of number is 15 lesser than twice the number.
[3 Marks]

Answer 1

Let the number be $x$.
Square of number: $x^2$
Lesser by 15: $x^2-15$
of two times the number: $x^2-15=2x$ [0.5 Marks]

We get, $x^2-15=2x$
Lets solve, $x^2-2x-15=0$ [0.5 Marks]
$x^2-5x+3x-15=0$ [0.5 Marks]
$x(x-5)+3(x-5)=0$
$(x-5)(x+3)=0$ [0.5 Marks]
$\therefore x=5\&x=-3$ [0.5 Marks]

The numbers satisfying the given statement are $5\&-3$. [0.5 Marks]