Question

expain using suitable identities (2x+3y-5z)²
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Answer 1

$(a+b+c)2= a2+b2+c2+ 2ab+2bc+2ca \\ or \\ (x+y+z)2= x2+y2+z2+ 2xy+2yz+2zx \\ here \: \: x = 2x \: and \: y = 3y \: and \: z = - 5z \\ (2x+3y-5z)² = (2x) {}^{2} + {(3y)}^{2} + {( - 5z)}^{2} + 2(2x)( 3y ) + 2( 3y )( - 5z) + 2(-5z)(2x) \\ (2x+3y-5z)² = 4 {x}^{2} + 9 {y}^{2} + 25 {z}^{2} + 12xy - 30yz - 20zx$