Quadratic Equation Form :
x2 = k
Where k > 0
If k is a positive number and if x2 = k,
then x = ±√k
Solve for x :
Example 1 :
x2 = 16
Solution :
x2 = 16
By taking square roots on both sides, we get
x
= √16
x = ± 4
So, the value of x is ± 4
Example 2 :
12x2 = 72
Solution :
12x2 = 72
Dividing by 12 on both sides, we get
x2
= 72/12
x2 = 6
By taking square roots
x = ± √6
So, the value of x is ± √6
Example 3 :
2x2 + 1 = 19
Solution :
2x2 + 1 = 19
Subtracting 1 on both sides,
2x2 = 18
Dividing by 2 on both sides.
x2
= 9
x = √9
x = ± 3
So, the value of x is ± 3
Example 4 :
2x2 + 7 = 13
Solution :
2x2 + 7 = 13
Subtract by 7 on both sides, we get
2x2 = 6
x2
= 3
x = ± √3
So, the value of x is ± √3
Example 5 :
3x2 = - 12
Solution :
3x2 = - 12
x2
= - 12/3
x2 = - 4
x = √-4
There is no real solution.
Example 6 :
1 – 3x2 = 10
Solution :
1 - 3x2 = 10
1 - 3x2 = 10
- 3x2 = 10 - 1
- 3x2 = 9
x2 = - 9/3
x2 = - 3
x = √-3
It has no solution.
Solve for x :
Example 7 :
(x – 2)2 = 9
Solution :
(x – 2)2 = 9
Taking the square root on both sides,
√(x – 2)2 = √9
x – 2 = ±3
x-2 = 3 x = 5 |
x-2 = -3 x = -1 |
So, the value of x is 5 or - 1.
Example 8 :
(x + 4)2 = 25
Solution :
(x + 4)2 = 25
Taking the square root on both sides,
√(x + 4)2 = √25
x + 4 = ±5
x+4 = 5 x = 1 |
x+4 = -5 x = -9 |
So, the value of x is 1 or - 9
Example 9 :
(x + 3)2 = - 1
Solution :
(x + 3)2 = - 1
Taking the square root on both sides,
(x + 3) = √- 1
So, there is no real solution.
Example 10 :
(x - 4)2 = 2
Solution :
(x - 4)2 = 2
Taking the square root on both sides,
√(x - 4)2 = √2
x - 4 = ± √2
x = 4 ± √2
So, the value of x is 4 ± √2
Example 11 :
(x + 3)2 = - 7
Solution :
(x + 3)2 = - 7
Taking the square root on both sides,
√(x + 3)2 = √- 7
x + 3 = √-7
So, there is no real solution.
Example 12 :
(x + 2)2 = 0
Solution :
(x + 2)2 = 0
Taking the square root on both sides,
√(x + 2)2 = √0
x + 2 = 0
x = - 2
So, the value of x is - 2
Example 13 :
(2x + 5)2 = 0
Solution :
(2x + 5)2 = 0
Taking the square root on both sides,
√(2x + 5)2 = √0
2x + 5 = 0
2x = - 5
x = - 5/2
x = - 2 1/2
So, the value of x is – 2 1/2
Example 14 :
(3x - 2)2 = 4
Solution :
(3x - 2)2 = 4
Taking the square root on both sides,
√(3x - 2)2 = √4
3x - 2 = ± 2
3x-2 = 2 3x = 4 x = 4/3 |
3x-2 = -2 3x = 0 x = 0 |
So, the value of x is 4/3 or 0
Example 15 :
1/3 (2x - 1)2 = 8
Solution :
1/3 (2x - 1)2 = 8
(2x – 1)2 = 24
Taking the square root on both sides,
√(2x - 1)2 = √24
2x - 1 = ± √24
2x = ± √24 + 1
x = ±(√24 + 1)/2
x = (1 ± 2√6)/2
So, the value of x is (1 ± 2√6)/2.
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