Question

Where does the parabola `x^2-3x=40` have roots?

Answer 1

`x=-5" and " x=8`

Explanation:

`"rearrange and equate to zero"`

`rArrx^2-3x-40=0`

`"splitting the middle term gives"`

`x^2-8x+5x-40=0`

`"factorising"`

`x(x-8)+5(x-8)=0`

`"taking out the factor " (x-8)`

`rArr(x-8)(x+5)=0larr" equate each factor to zero"`

`x-8=0rArrx=8`

`x+5=0rArrx=-5`

`rArrx=-5" and " x=8" are the roots"`
graph{x^2-3x-40 [-10, 10, -5, 5]}