heres the question: sketch the curve of y=4-7x-2xsqrd
i get y=4, but to get the two x roots i factorise as normal, and get the solutions x=1/2 and x=+4
however the textbook says that the second root is actually -4...
why?
for easiness i will make this smiley face the sign for squaredNod)
sketch curve of y=4-7x-2x
1) a<0 (-2) so curve is inverted u shape
2) find where it crosses y axis:
subst x=o into eqn
y=4
3)factorise to find the two roots of the curve
0=-2x-7x+4
0=-2x-8x+x+4
-2x(x-4) 1(x-4)
(-2x+1) (x-4)=0
1)x-4=0
x=4
2)-2x+1=0
x=1/2
so x=1/2 and x=4
so why is it -4?