Question

who know the answer with solution only they will give the answer if not don't need to give answer and then alsoyou will give the answer I will report your answer. Thank you

Answer 1

Hey User✋

Answer Of Your Question (:

(20)

R.H.S

(7x+1/2)(7x-1/2)

=(7x)^2-(1/2)^2 [because :- (a+b)(a-b)=a^2-b^2]

=49x^2-1/4

So, Comparing the value ,

answer comes= 1/4

So, answer is=(c)1/4
____________________________
(21)if a+b+c=0 then a^3+b^3+c^3=?

Solution,

a^3+b^3+c^3

=(a+b+c)(a^2+b^2+c^2-ab-bc-ca)

=3abc [Because:-(a+b+c=0)]

so, option (c)3abc is correct

Hope My Answer Helped

Answer 2

$20. \: given - - > \: 49 {x}^{2} - b = (7x + \frac{1}{2} )(7x - \frac{1}{2} ) \\ \\ solving \: rhs - - > \\ (using \: formula \: {a}^{2} - {b}^{2} = (a - b)(a + b)) \\ \\ = > (7x + \frac{1}{2} )(7x - \frac{1}{2} ) \\ = > ( {(7x)}^{2} - {( \frac{1}{2} )}^{2} ) \\ = > 49 {x}^{2} - \frac{1}{4} \\ \\ comparing \: lhs \: with \: rhs \: we \: get \\ b = \frac{1}{4} \\ \\ ans \: is \: option \: c. \frac{1}{4}$

21. $given - - > a + b + c = 0 \\ \\ identity - - > {a}^{3} + {b}^{3} + {c}^{3} - 3abc = (a + b + c)( {a}^{2} + {b}^{2} + {c}^{2} - ab - bc - ac) \\ \\ now \: from \: this \: we\: get \\ {a}^{3} + {b}^{3 } + {c}^{3} - 3abc = 0 \\ \\ {a}^{3} + {b}^{3 } + {c}^{3} = 3abc \\ \\ ans \: is \: option \: c. \: 3abc$