Find 21- 23- using a suitable algebraic identity-

We know that, nbsp; 21 × 23 can be written as (20 + 1) × (20 +3) So, using the algebraic identity, nbsp;(x + a) × (x +b)= x^2 + (a+b)x+ab Here, x = 20, a = ...

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Standard VIII

Mathematics

Factorization of ax^2+bx+c

Find 21× 23, ...

Question

Find $21 \times 23$ , using a suitable algebraic identity.
483

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Solution

The correct option is A 483
We know that,
$21 \times 23$ can be written as $(20 + 1) \times (20 + 3)$
So, using the algebraic identity, $(x + a) \times (x + b) = x^{2} + (a + b) x + a b$

Here, $x = 20, a = 1, b = 3$
$(20 + 1) \times (20 + 3) = 20^{2} + (1 + 3) \times 20 + 1 \times 3$
$= 400 + 80 + 3$
$= 483$

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Find 21×23, using a suitable algebraic identity. 483

The correct option is A 483We know that, 21×23 can be written as (20+1)×(20+3) So, using the algebraic identity, (x+a)×(x+b)=x2+(a+b)x+ab Here, x=20,a=1,b=3 (20+1)×(20+3)=202+(1+3)×20+1×3 =400+80+3 =483

Find $21 \times 23$ , using a suitable algebraic identity.
483