实数x,y满足x^2+y^2=4,则x^2+8y+3的最大值是?

实数x,y满足x^2+y^2=4,则x^2+8y+3的最大值是?
实数x,y满足x^2+y^2=4,则x^2+8y+3的最大值是?

实数x,y满足x^2+y^2=4,则x^2+8y+3的最大值是?
x^2+y^2=4
x^2=4-y^2
x^2+8y+3
=4-y^2+8y+3
=-y^2+8y-16+23
=-(y-8)^2+23
因为-(y-8)^2≤0
所以x^2+8y+3的最大值是23