How do you solve the equation by graphing # 3x^2 + 9x = 12#?

1 Answer
MeneerNask
Mar 15, 2016

You could graph the function and intersect it with a horizontal line at #y=12#

Explanation:

On your GC you would use #Y_1=3x^2+9x# and #Y_2=12#
And then the intersect -function. Make sure you set the windows at the right values. This usually takes some trying.

Easier:
At first we can divide everything by #3#
#->x^2+3x=4#
Then subtract #4# on both sides:
#->x^2+3x-4=0#
You can factor this into:
#->(x-1)(x+4)=0#
So:
#->x-1=0->x=1#
#orx+4=0->x=-4#

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