posted by Jenny on .
i forgot how to solve these types of problems..
2x^2-18x=0, x^2=6x+7, 6y^2+5y-6=0
SOLVE FOR X CORRECT TO 4 DECIMAL PLACES:
For the first bit of the question, get all the terms over onto the left-hand side of the equation. For example, take the second one:
Usually you can factorize it easily into the following form: (X+A)(X+B). (There's no guarantee that it's an easy factorization, but if you're expected to solve it this way it usually is.)
If you multiply out those two brackets, you'll get X² + (A+B)X + AB.
So in this example, if you compare the corresponding terms from the two equations, A + B = -6 and AB = -7. So what are A and B? Usually you can spot it in a few seconds...
How about A = 1 and B = -7?
One down, two to go...