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Solving the Quadratic Equations
Let’s learn further by solving the equations of the above question.
X2 + 12 = 7X
Taking 7X to left side, we get X2 – 7X + 12 = 0
In this, a = 1, b = -7 and c = 12
Also, sum of roots = -b/a = 7; product of roots = c/a = 12
To arrive at the roots, we’ll have to split up the middle term. We’ll have to break 7X into two parts, let’s say, pX and qX, in such a way that
p+q should be = b = -7, and, pq should be = c*a = 21*1 = 12
If we break -7X into -4X and -3X
(-4)+(-3) = -7
(-4)(-3) = 12
Which is the desired thing. Thus, our equation becomes.
X2 – 4X – 3X + 12 = 0
X[X – 4] – 3[X – 4] = 0
[X – 4][X – 3] = 0
X = +4 and +3
Which is the solution of this quadratic equation. This equation can also be solved using the discriminant method.
D = b2 – 4ac = (-7)2 – 4*1*12 = 49 – 48 = 1
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You have to decide which process is faster. Splitting up the middle term requires a lot of practice. Discriminant method is slow, but effective. You don’t have to worry about in what way the middle term should be split.
Solving 2nd equation.
Y2 + 30 = 11Y
Y2 – 11Y + 30 = 0
Y2 – 6Y – 5Y + 30 = 0
Y[Y – 6] -5[Y – 6] = 0
[Y – 6][Y – 5] = 0
Y = +6 and +5
Discriminant method will also give you the same result.
Solving The Question
So far we have solved only the equations. The final part that remains solving is: what is the relation between X and Y?
To solve this, you have to bear in mind three things:
The relation between 1st root of X to both the roots of Y
The relation between 2nd root of X to both the roots of Y
Both the above relations should match!
To do this, check the relation between both the roots of the equations one by one.
X = +3, +4
Y = +5, +6
+3 is less than or greater than +5 and +6?
Less than.
+4 is less than or greater than +5 and +6?
Less than.
Both relations are same. So, final answer is: X is less than Y.
TableSolving the Quadratic EquationsLet’s learn further by solving the equations of the above question.X2 + 12 = 7XTaking 7X to left side, we get X2 – 7X + 12 = 0In this, a = 1, b = -7 and c = 12Also, sum of roots = -b/a = 7; product of roots = c/a = 12To arrive at the roots, we’ll have to split up the middle term. We’ll have to break 7X into two parts, let’s say, pX and qX, in such a way thatp+q should be = b = -7, and, pq should be = c*a = 21*1 = 12If we break -7X into -4X and -3X(-4)+(-3) = -7(-4)(-3) = 12Which is the desired thing. Thus, our equation becomes.X2 – 4X – 3X + 12 = 0X[X – 4] – 3[X – 4] = 0[X – 4][X – 3] = 0X = +4 and +3Which is the solution of this quadratic equation. This equation can also be solved using the discriminant method.D = b2 – 4ac = (-7)2 – 4*1*12 = 49 – 48 = 1Capture You have to decide which process is faster. Splitting up the middle term requires a lot of practice. Discriminant method is slow, but effective. You don’t have to worry about in what way the middle term should be split.Solving 2nd equation.Y2 + 30 = 11YY2 – 11Y + 30 = 0Y2 – 6Y – 5Y + 30 = 0Y[Y – 6] -5[Y – 6] = 0[Y – 6][Y – 5] = 0Y = +6 and +5Discriminant method will also give you the same result.Solving The QuestionSo far we have solved only the equations. The final part that remains solving is: what is the relation between X and Y?To solve this, you have to bear in mind three things:The relation between 1st root of X to both the roots of YThe relation between 2nd root of X to both the roots of YBoth the above relations should match!To do this, check the relation between both the roots of the equations one by one.X = +3, +4Y = +5, +6+3 is less than or greater than +5 and +6?Less than.+4 is less than or greater than +5 and +6?Less than.Both relations are same. So, final answer is: X is less than Y.
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