求x:(1)9x²-25=0 (2)¼(x+3)²=9 (3)8x²+125=0 (4)8(x+5)³-27=0
问题描述:
求x:(1)9x²-25=0 (2)¼(x+3)²=9 (3)8x²+125=0 (4)8(x+5)³-27=0
答
(1)9x²-25=0(3x+5)(3x-5)=0 (平方差公式)x=-5/3或x=5/3(2)(1/4)(x+3)²=9(x+3)²-36=0 (x+3+6)(x+3-6)=0 (平方差公式)(x+9)(x-3)=0x=-9或x=3(3)8x²+125=...