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put this solution on YOUR website! 15x²+8x-12 = 0
Use the "AC" method:
Multiply 15 by 12, first and last numbers.
15×12 = 180
Look for two factors of 180 that differ by 8, the middle coefficient.
Doesn't take long to see that they are 18 and 10.
Give them signs necessary to form middle coefficient +8.
That is, +18-10 equals +8
So we write 15x²+8x-12 = 0 as
15x²+18x-10x-12 = 0
Factor the first two terms by taking out 3x
3x(5x+6)-10x-12 = 0
Factor the last two terms by taking out -2
3x(5x+6)-2(5x+6) = 0
Factor the whole left side by taking out (5x+6)
(5x+6)(3x-2) = 0
Set each factor = 0
5x+6=0; 3x-2=0
5x=-6; 3x=2
x=-6/5; x=2/3
Edwin
