

Key Concepts for Quadratic Equation: A quadratic polynomial, when equated to zero, becomes a quadratic equation. In other terms, a quadratic equation is a second-degree algebraic equation. The values of x satisfying the equation are called the roots of the quadratic equation.
General form: a x 2 +bx+c=0 where x represents an unknown, and a, b, and c are constants with a not equal to 0 . The constants a, b, and c are usually real numbers, but they can be complex numbers as well. Quadratic equation examples: x 2 +5x+6=0 , 6 x 2 -17x+12=0
The Quadratic Equation Formula expresses the solutions in terms of a , b , and c .
1) I. x2-9x+20=0 II. y2-7y+12=0
Solution:
I. x 2 -9x+20=0 x 2 -4x-5x+20=0 x(x-4)-5(x-4)=0x=4,5
II. y 2 -7y+12=0 y 2 -4y-3y+12=0 y(y-4)-3(y-4)=0y=4,3
Case 1: x = 4, x = 4 (x = y)
Case 2: x = 4, x = 3 (x > y)
Case 3: x = 5, x = 4 (x > y)
Case 4: x = 5, x = 3 (x > y)
So, x y2) I. x2-5x-14=0 II. y2-16y+64=0
Solution:
x=7,-2
y=8,8
Case 1: x = 7, y = 8 (y > x) Case 2: x = 7, y = 8 (y > x) Case 3: x = -2, y = 8 (y > x) Case 4: x = -2, y = 8 (y > x) So, x<y3) I. x2 + 7x+12=0 II. y2+9y+20=0
Solution:
I . x 2 + 7x+12=0 x 2 +4x+3x +12=0 x(x + 4)+3(x+4) = 0 (x +4) (x +3)=0 x = -3, -4Solving quadratic equations tips and tricks are given in this section.
Trick 1: Quadratic equations solution based on the sign of coefficients in the equation:
For example:
In this example, the signs visible in the x equation are ( -, +) and signs visible in the y equation are (+, +). So, signs of actual value of x and y in the final answer will be ( +, +) and ( -, -) So, “ Relationships can’t be established”.
Solution:
I . x 2 - 14x+45= 0 x 2 - 9x-5x+45= 0 x(x -9)-5(x-9)=0 x = 9, 52) I. x2 + 32x + 240 = 0
Solution:
From I: x 2 + 32x + 240 = 0 x 2 + 20x + 12x + 240 = 0 x(x + 20) + 12(x + 20) = 0 (x + 20)(x + 12) = 0 x = -20, -12 From II: y 2 + 3y – 108 = 0 y 2 + 12y – 9y – 108 = 0 y(y + 12) – 9(y + 19) = 0 (y + 12)(y – 9) = 0 y = -12, 9 Case 1: x = -20, y = -12 ( y > x) Case 2: x = -20, y = 9 (y > x) Case 3: x = -12, y = -12 ( x = y ) Case 4: x = -20, y = 9 (y > x) So, y ≥ x3) I. 6x² + 19x + 15 = 0
Solution:
4) I. 2x2- x - 1=0
Solution:
From equation I 2x 2 -x-1=0 2 x 2 -2x+x-1=0 2x(x-1) +1(x-1)=0 (2x+1) (x-1)=0 x= -1 2 , 1 From equation II 2y 2 - 4y +2=0 2y 2 - 2y - 2y +2=0 2y(y-1)- 2(y-1)=0 (2y-2) (y-1)=0 y = 1, 1 Case 1: x = -½, y = 1 (y>x) Case 2: x = -½, y = 1 (y>x) Case 3: x = 1, y = 1 (y=x) Case 4: x = 1, y = 1 (y=x) So, x ≤ y5) I . 4x2- 7x - 57 =0
II. 5y 2 - 6y - 63=0Solution:
From equation I 4x 2 -7x - 57 =0 4x 2 -19x+12x-57 =0 x(4x-19) +3(4x-19) =0 (4x-19) (x+3) =0 x= 19 4 ,-3 From equation II 5y 2 - 6y - 63=0 5y 2 -21y+15y-63 =0 y(5y-21) +3(5y-21) =0 (y+3)(5y-21)=0 y = -3, 21 5 Case 1: x = 19 4 , y = -3 (x > y) Case 2: x = 19 4 , y = 21 5 (x > y) Case 3: x = -3, y = -3 (x = y) Case 4: x = -3, y = 21 5 (y > x) So, x = y or relationship between x and y can't be established.| Related Links | |
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