Very short answer type questions (1 -
2):
1. Find the roots of the following quadratic equations by factorisation:
() x-3x- 10 = 0
(ii) 6x2 + X-2 9
(i) 2x2+x- 6 = 0
(iv) 6x2+7x-10 = 0
(U) 8x2-22x-21 (vi) 2x2+x-2 = 0
2. Find the roots of the follow, quadratic equations by factorisation
1 (i) 121x2-22x +1 0 (ii) 21x2-2x+ . =0
21
(iv) +2 = 0, x #0 2 5 (iii) . -10 = 0
15 3
3. Find the roots of the following quadratic equations by factorisation
(i) 3x2+5V5x- 10 = 0 (NCERT Exem1plar) (it) 2 3 12-5x+ v3=0
(ii) x2-35x+ 10= (CBSE 2017) (iv) 4 3 12+ 5x -23 =0
Answers
What's the question?
Can't figure out
Answer:
The roots of quadratic equation are the values of the variable that satisfy the equation. They are also known as the "solutions" or "zeros" of the quadratic equation. For example, the roots of the quadratic equation x2 - 7x + 10 = 0 are x = 2 and x = 5 because they satisfy the equation. i.e.,
when x = 2, 22 - 7(2) + 10 = 4 - 14 + 10 = 0.
when x = 5, 52 - 7(5) + 10 = 25 - 35 + 10 = 0.
But how to find the roots of a general quadratic equation ax2 + bx + c = 0? Let us try to solve it for x by completing the square.
ax2 + bx = - c
Dividing both sides by 'a',
x2 + (b/a) x = - c/a
Here, the coefficient of x is b/a. Half of it is b/(2a). Its square is b2/4a2. Adding b2/4a2 on both sides,
x2 + (b/a) x + b2/4a2 = (b2/4a2) - (c/a)
[ x + (b/2a) ]2 = (b2 - 4ac) / 4a2 (using (a + b)² formula)
Taking square root on both sides,
x + (b/2a) = ±√ (b² - 4ac) / 4a²
x + (b/2a) = ±√ (b² - 4ac) / 2a
Subtracting b/2a from both sides,
x = (-b/2a) ±√ (b² - 4ac) / 2a (or)
x = (-b ± √ (b² - 4ac) )/2a
This is known as the quadratic formula and it can be used to find any type of roots of a quadratic equation.