Tìm x, y, biết: a) x^2 +7x = 8 b) 2x^2 +4y^2 +10x + 4xy = -25
Giải thích
a)
x2+7x=8x2+7x−8=0x2+8x−x−8=0xx+8−x+8=0x−1x+8=0⇒x−1=0x+8=0⇒x=1x=−8
Vậy x∈−8; 1
b)
2x2+4y2+10x+4xy=−252x2+4y2+10x+4xy+25=0x2+10x+25+x2+4xy+4y2=0x+52+x+2y2=0
a)
x2+7x=8x2+7x−8=0x2+8x−x−8=0xx+8−x+8=0x−1x+8=0⇒x−1=0x+8=0⇒x=1x=−8
Vậy x∈−8; 1
b)
2x2+4y2+10x+4xy=−252x2+4y2+10x+4xy+25=0x2+10x+25+x2+4xy+4y2=0x+52+x+2y2=0