Question

解方程用降次：(1)、4x²=81,(2)、(x+5)²=25,(3)、x²+2x+1=4

Answer 1

(1)

4x^2=81

x^2=81/4

x = ±3√3/2

(2)

(x+5)^2=25

x+5=±5

x=10 or 0

(3)

x^2+2x+1=4

x^2+2x-3=0

(x+3)(x-1)=0

x=-3 or 1