Seratul Seratul

26-02-2017
Mathematics

contestada

If [tex] x^{2} -y^{2} =21 [/tex], then [tex]2(x+y)(x-y)=[/tex]

A. 21/2
B. 18
C. 21
D. 42
Please explain.

Respuesta :

ChandrikaP ChandrikaP

26-02-2017

Answer is D 42
[tex] x^{2} - y^{2} =(x+y)(x-y) [/tex]
It is given
=21
Multiply both side by 2
U will bet 21×2=42

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