# Quadratic graph; solving equations.

• Jan 27th 2010, 01:20 PM
vanklik
Quadratic graph; solving equations.
Hi, I hope someone will help me! I've got a graph of x2+3x=8 (quadratic). By drawing a suitable straigt line on the graph, I need to solve the equation: x2+2x-4=0 (quadratic) How do I draw the second graph without solving the equation first?
Thank you for your help!
• Jan 27th 2010, 02:33 PM
$x^2+2x-4=(x^2+3x-8)-(x-4)$
Therefore you can solve $x^2+2x-4=0$ by solving $(x^2+3x-8)-(x-4)=0$
In other words, by finding where the line $x-4$ crosses the curve $x^2+3x-8$