Question

The cost,C, of manufacturing and selling s units of a product is C=23x+70, and the corresponding revenue, R, is R=x^2-70. Find the break-even value of x.

Answer 1

`23x+70=x^2-70\\ x^2-23x-140=0\\ x^2+5x-28x-140=0\\ x(x+5)-28(x+5)=0\\ (x-28)(x+5)=0\\ x=28 \vee x=-5`

x can't be negative so
`x=28`