Substitute x=14\displaystyle x = \frac{1}{4}x=41 into 1+x1−3x=1+2x+4x2\displaystyle \sqrt{\frac{1+x}{1-3x}} = 1 + 2x + 4x^21−3x1+x=1+2x+4x2 to obtain an approximation for 5\sqrt{5}5. Give your answer as a fraction in its simplest form.
408 exam-style questions on Edexcel A Level Maths Binomial Expansion, covering 4.1 Expanding (1 + x)^n, 4.2 Expanding (a + bx)^n, and 4.3 Using Partial Fractions. Each one has a worked solution and a mark scheme showing where the marks go.