√x + √(x+7) + 2√(x^2+7x) = 35-2x
√x + √(x+7) + 2√(x(x+7)) = 35-2x
2x + 2√(x(x+7)) + (√x+√(x+7)) = 35
x + 2√x√(x+7) + (x+7) + (√x+√(x+7)) = 35+7
(√x)^2 + 2√x√(x+7) + (√(x+7))^2 + (√x+√(x+7)) = 42
(√x+√(x+7))^2 + (√x+√(x+7)) - 42 = 0
解得
√x+√(x+7) = -7或√x+√(x+7)=6
因?yàn)椤蘹+√(x+7) > 0故√x+√(x+7)=6
√(x+7)=6-√x
兩邊同時平方得:
x+7 = 36-12√x + x
化簡得12√x = 29
x=841/144
因?yàn)槲页３沐e,所以不知道結(jié)果是否正確,反正方法就是這樣的..