X^2+x-12=0 factors out into (x+4)(x-3) so the answer is: x=-4, x=3
Explanation:
Basically, you can do it in many ways. But just, in my opinion, exactly linear algebra was made for such cases.
the optimal way is to do it with Cramer's rule.
First, find the determinant and then find the determinant x, y, v, u.
Afterward, simply divide the determinant of variables by the usual determinant.
eg. 
and etc.
I think that is the best way to solve it without a hustle of myriad of calculations reducing it to row echelon form and solving with Gaussian elimination.
80 square units
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The Formula for the area of a trapezoid is A= (a+b/2)h
A= 3+17/2 (8)
A= 20/2 (8)
A= 10 (8)
A = 80
A terminating decimal has digits that end. They do not go on forever. For example, 0.125 has only 3 decimal digits and does not keep on going like 1/3
A rational number is a number that canbe expressed as p/q where p and q are both integers. But q cannot equal to 0.
All terminating decimals are rational numbers, but not all rational numbers are terminating decimals. For example 1/4, which equals to 0.25 is both a rational number and a terminating decimal. On the other hand, 1/3 is a rational number but is not a terminating decimal.
This can be calculated easily.
As any two digit number can be written in the following form:
N= 10x +y
If we reverse the number now, it would become:
N' = 10y + x
So if we subtract one from the other, we should obtain 18 ( as mentioned in the question ).
N-N'= 18
=> x-y = 2
Thus, any number whose digits differ by two would be an aswer to the question.
The only numbers which satisfy this are : 13,24,35,46,57,68,79
But this would not be true for any 3 or more digit number.
