I need help with a function question please

My daughter is working on the following question:

Find the equation of a line that passes through the origin and point (-3, 6). According to the answer book, the answer is y = -2x

Would someone be able to tell me how to solve this question to get this answer.

Thank you

The of this line is m=(6-0)/(-3-0)=-2
The point-slope equation is
y-0= -2(x-0)
y= -2x

so if you use the formula y=mx+b you can assume that b is zero because the line passes through the origin. so then plug in the point -3,6 so that 6= -3m. the divide by -3 and you get -2. therefore, -2 is m, or the slope. if you plug it back in you get y=-2x

the complete equation for 2 points line is:

y-y1 = m(x-x1)

where gradient m = (y2-y1)/(x2-x1)

x1,y1= 0,0 --> origin is 0,0
x2,y2= -3,6

y-y1= m (x-x1)
y-0 = (6-0)/(-3-0) (x-0)
y = -2x

for other points, just subtitute the x1,y1 and x2,y2 values..
hope this helps...