Respostas
Explicação passo-a-passo:
a) x²-36=0
x²=36
x= +- raiz de 36
x= +-6
x¹= +6 S={ 6,-6} /\>0 => 2 raízes
x²= -6
b) x²+7x=0 a=1
b=7
c=0
/\=b²-4ac x= -b+- raiz de delta/2
/\=(7)²-4×1×0 x= -(7)+-raiz de 49 /2
/\=49-0 x= -7+-7 /2
/\=49
x¹=-7+7/2 => x¹=0/2 => x¹=0
x²= -7-7/2 => x²= -14/2 => x²= -7
/\=0 => raiz nula
c) 2x²-72=0
a=2 /\=b²-4ac
b=-72 /\=(-72)²-4×2×0
c=0 /\=5184
x= -b+- raiz de delta/2a
x= -(-72)+-72/2×2
x= 72+-72/4
x¹=72+72/4 => x¹= 144/4 => x¹= 36
x²= 72-72/4 => x²=0/4 => x²=0
S={ 36,0}
d)2x²-8x=0
a=2 /\=b²-4ac
b=-8 /\=(-8)²-4ac
c=0 /\=64-4×2×0
/\= 64
x= -b+- raiz de delta /2a
x= -(-8) +- 8 /2×2
x= 8 +-8/4
x¹= 8+8/4 => x¹=16/4 => x¹=4
x²=8-8/4 => x²=0
S={4,0}
Espero ter ajudado!