将函数y=sin2x+cos2x的图像向左平移派/4个单位,所得图像的解析式是?

平移后
y=sin2(x+pi/4)+cos2(x+pi/4)
=sin(2x+pi/2)+cos(2x+pi/2)
=cos2x - sin2x
= sqrt2 (cospi/4 cos2x-sinpi/4 sin2x)
= sqrt2 cos(2x+pi/4)